Ducati Monster Forum

Ok, I recently had a Nichols lightweight flywheel installed on my 1098.  It was a beautiful change all around.  The bike transitions smoother/faster, it rides muuuuch smoother at low RPMs in 1st, and the acceleration is a bit better all around.  The only downside is a small increase in revs to get going in 1st.  Oh, and the bike revs like crazy.

SO, after like 5 short rides around town with the new flywheel, I accidentally bump the bike into 1st at a stoplight and it stalls.  I go to start the bike back up and it makes really LOUD nasty clacking/banging noises and takes 5+ tries to start now.  The really odd thing is that the bike runs great once it starts up and nothing out of the ordinary.  It is only when I go to start it up that it sounds awful from the starting system.

I took the bike back to the shop who did the work to have them look at it and have the starter/sprag/whatever repaired under warranty.  DNA tells the shop the lightweight flywheel caused damage to the sprag.  Under the Magnuson-Moss 'Warranty' Act, the dealer or manufacturer must prove the aftermarket item caused the damage.  So far, I've spoken with several other Ducati dealerships and aftermarket shops who've all said a lightweight flywheel should not cause damage to the sprag or starting system.  If anything, it will reduce the lifespan, but I only have 5,500 miles on the bike!  This is a lifespan of a part that is supposed to last like 30,000 miles.

SO, any advice for how to approach this situation.  If the flywheel genuinely caused the damage, not a mistake during installation (cock-eyed assembly or whatever), I'm happy (begrudgingly) to pay the bill and man up.  However, if there is no way the flywheel actually caused the damage and there is something wrong with my bike Ducati is refusing to cover under warranty, I'm going to be a bit pissed if I have to fight this.

The fact that Ducati sells a lightweight flywheel as an aftermod, brings into question their statement that lightweight flywheels cause sprag clutch failures.

Trust me, I've been through this for a transmission on what was at one time, my new car. I'll tell you the best way to handle this.

Go to another dealer. Its that simple. Some dealers are assholes and their representatives have been trained to spit out jibberish. If you have other dealers near your go to them first before you argue with Ducati. But at the same time, be prepared to ride it through to the end. It may take some time.

Laws are fine and dandy but unless you yourself are a lawyer, its going to cost you more money and time to settle the matter legally than to just explore your options and settle accordingly. Experiences with DNA (Ducati North America) have gone both ways so but most of the time they are reasonable.

1) Another Dealer
2) Appeal to DNA directly
3) Get a lawyer to write a letter to the dealership
4) Become a greasemonkey and do it yourself.

A light flywheel does not damage a sprag. I've run & sold LOT'S of light flywheels over many thousands of miles & 10 or so years & have never experienced or even heard of a related problem.

I've had an "Ebay Special" light light ligghhttt weight flywheel on my bike for about 6k with no probs... Something prob went wrong with install. It's common for people who don't know what they are doing to screw up the little details like a special nut inside there and washers to be changed out... Look into it, good luck.

Christopher

Well, I ended up having to pay $400 after wating 6 months to get this shit sorted.  I'll be finding a reliable mechanic and a good dealership and not screw with another lightweight flywheel until I have a nemesis and full system on the bike.  After the warranty runs out, I'll definitely NOT be renewing it.  Right now the bike takes 4+ tries to start unless I give it some throttle.

Soo - you looking for a home for that poor flywheel?

Quotea lightweight flywheel should not cause damage to the sprag or starting system.  If anything, it will reduce the lifespan,

Did they explain why lifespan is reduced?

QuoteI ended up having to pay $400 after wating 6 months to get this shit sorted.

How was it sorted, new sprag w old flywheel or what?
Was the original sprag worn?


I think a lw flywheel have some impact on starting,
having like only 25% of the weight must do something,
maybe harder to get past TDC 1st revolution or what do you guys think?

I can't imagine a light weight flywheel having any impact on the sprag.  There may be a very slight possibility of it affecting the engagement of an already failing sprag.

I can't imagine the flywheel doing any damage to the sprag.

On the flip side, I can imagine a mechanic damaging the sprag installing the flywheel incorrectly. Isn't the the sprag is right behind it...

Quote from: greenmonster on December 16, 2008, 11:41:56 AM
Did they explain why lifespan is reduced?


How was it sorted, new sprag w old flywheel or what?
Was the original sprag worn?


I think a lw flywheel have some impact on starting,
having like only 25% of the weight must do something,
maybe harder to get past TDC 1st revolution or what do you guys think?

The 'solution' was to go back to stock so I'd have future warranty coverage should my motor explode in the future.  I don't have the time or money to pay a lawyer to explain the Magnuson-Moss Act in bold legal font, so I'm just not going to bother modifying the bike until the warranty runs out and I hopefully get this ridiculously underpowered starting system replaced under warranty.  The 4+ starting attempts is with the STOCK flywheel.  After the lightweight flywheel was installed, it took maybe 2-3 tries.

DNA's explanation of why the sprag was damaged by the flywheel was some bullshit about a lawnmower with no blade on it...  I told the shop that is an irrelevant example and fails to prove the flywheel caused the damage, but trying to have my semi-mechanically ignorant wife explain things to them while I was half a country away was getting old fast and I just wanted my bike back.  The fact that DNA only covered the cracked bracket under warranty tells me either DNA or the shop in question had no interest in giving me fair honest service.  I was told by the shop the sprag would not cause damage or affect my warranty and when that turned out to be either a flat-out lie or plain ignorance, I got screwed.  Lesson learned, I won't be dealing with a shop unless I know the mechanics personally and know they'll go to bat for me.  If the dealership in Dallas DID go to bat for me like they said they were, I have zero trust in Ducati North America when it comes to warranty issues. 

Oh, and I never got my flywheel back from them.  The last time I had the bike worked on and was told I had the wrong battery in the bike, they went ahead and charged me for the proper size battery and recycled my BRAND NEW battery without even asking me if I wanted it back.  SO, I seriously doubt they have the flywheel at this point, and even if they do, they'd probably make up some story about how it got pitched because they assumed I didn't want my $200ish part back.

So, long story short, after the nichols flywheel was on the bike, it started and ran beautifully, but after accidentally bumping the bike into 1st at a stoplight (without my hand on the clutch lever) it fragged my sprag.  Whether this was due to it being a lightweight flywheel, an 'oops' on the dealer's install, or simply the fact that the stock ducati parts are ridiculously fragile, I'll never know.  I've accidentally bumped my speed triple into gear at lights probably 5+ times over the past 20,000 miles without ANY starting or clutch issues, so this makes me lean toward weak parts or a bad install.

Hopefully, I don't run into any more bullshit with this bike.  I love Ducatis, but if I have future issues with DNA or my bike's starting system crapping out, I don't know that I'll buy another.  Thats too bad too because the new Streetfighter looks sick.

Quote from: Drunken Monkey on December 16, 2008, 11:36:37 PM
I can't imagine the flywheel doing any damage to the sprag.

On the flip side, I can imagine a mechanic damaging the sprag installing the flywheel incorrectly. Isn't the the sprag is right behind it...

The outer driven part of the sprag is bolted to the flywheel, the whole sprag assembly would have been 'disturbed' during the fitting of the light flywheel.
IMHO the subsequent failure was attributable to the installation not the effect of the flywheel itself.

QuoteSo, long story short, after the nichols flywheel was on the bike, it started and ran beautifully, but after accidentally bumping the bike into 1st at a stoplight (without my hand on the clutch lever) it fragged my sprag.

This is the hard part to swallow.
If that is really true, mustn`t there been bad shop install here? Sounds like BS to me.

Wait wait wait.

Do I understand this correctly?

You took a perfectly running 1098 to a ducati dealer to have a nichols mfg flywheel installed
Shop installs flywheels, away you go
Bike breaks shortly afterwards, sprag gear is broken
Shop says there is nothing they can do about it, and charges you more money to fix it?

WTF over.  How to "shops" continue to stay in business that pull this kind of shit.  I'm sorry to say, but over half of the "dealers" I've been to don't have a freaking clue when it comes to mechanicals on the bike.  And to make matters worse, if you call to ask advice or a simple question, you get a cocky smart ass remark like "yes I know I'm right, I do this for a living". (funny when you yourself are looking at that part while speaking with them, and they are dead wrong....but I've digressed)

make the beast with two backs that.  Take them to small claims court.   The freakin dealer should be standing behind what they did.  I'm so pissed, and it's not even my bike/situation.  I'm just tired of hearing about people getting boned out of $$

Tell'em you want your freak'n flywheel back or fork over $200.00.  Hell, tell you want your damn installation money back too.  They assumed liability for proper function when they took you money.  You've got the paper work to prove it.

Good points.  If they believed the lighted flywheel would harm the sprag or void your warranty you should have been informed in advance of doing the work, therefore it is their responsibility IMO (since I am not a lawyer do not take this as legal advice).

This is a known problem and an issue that you should consider before you add a lightweight flywheels to a Ducati. Ducati sees a lot of worn-out starter clutches when there is a very light flywheel attached. Why? Often lighter flywheels seem to let the engine kick-back much harder during start-ups and shut-downs, which causes starter clutch damage.



Why You Have a Flywheel

A lightened flywheel is one modification to a STREET bike that will have more negative than positive effects. I left mine stock. Here’s why.

An engine makes the least torque at idle and low rpm, especially when cold (when there are more misfires.) So when you release your clutch a little too fast, the engine torque is too small to overcome the bike's inertia, and it stalls. If you have a flywheel, the stored momentum augments the engine's torque allowing you to use a lower rpm starting-off. Without a flywheel you'd need a higher idle speed, or constantly need to start-off at a higher rpm in order to raise the engine torque output enough to avoid stalling the engine.

As you ride at lower rpm in traffic, you are constantly changing between acceleration and deceleration. Engine torque levels are still fairly low at these speeds, so slack in the drive train needs to be smoothed-out with a flywheel. Otherwise, on-off throttle transitions have a jerky effect, giving a less comfortable ride and causing you to use smaller throttle inputs (which is not always easy to do.)

At higher speeds a flywheel slows the rate at which an engine rpm changes, so cracking the throttle open or closed results in a smoother transition in torque being applied to the drive train and tires. Again, without a flywheel more careful throttle transitions are needed. The key to faster track times is reduced wheel spin so a light flywheel works against you by making it more difficult to modulate wheel spin, even though it helps lap times by producing more acceleration in the straights.

So in effect, a flywheel slows an engine's ability to change rpm producing drive train smoothness and drivability. It also reduces the engine's ability to match it's rpm with the drive train's rpm making it more difficult to downshift without producing wheel-hop.

And, when you miss a shift you’ll be glad you have one ...


Lightweight Flywheel - Pros and Cons

The weight of the stock flywheel is derived by Ducati test riders to provide an overall balance between performance and smooth drive train behavior. That's why Ducati selected the flywheel weight that they did. Did you think that they meant to purposely cripple the bike's performance by using a too-heavy flywheel?

When you remove weight from the flywheel (and to a lesser degree, from the clutch) the effect on the engine’s ability to more quickly spin-up is indistinguishable from increasing your engine’s torque (and consequently horsepower) output.

But only in neutral. In any other gear, there’s little benefit at all.

Obviously, your bike’s ability to accelerate faster through the gears is enhanced by reducing the overall weight of the bike as well as the inertia of rotating components. The crankshaft, pistons and connecting rods, transmission gears, drive chain and sprockets, wheels and tires, clutch and flywheel are all candidates.

However, the overall weight of the bike and rider completely overwhelms any reduction of rotational inertia produced by a lighter flywheel. A two pound lighter flywheel on a 600 pound bike-plus-rider will accelerate only 0.3% faster. F=ma.

Of course every 0.3% helps a racebike. When you reduce weight you’ll get faster acceleration, and faster lap times - IF - you can modulate your wheel spin driving out of corners. Factory racebikes make so much power, for example, that transmitting the power to the road effectively becomes the limiting factor - so heavier flywheels actually become a benefit. Fear the high-side.

The ability of an engine with a lightened flywheel to SPIN-UP more quickly is often pointed-to as a benefit when you bang a downshift and wheel hop is reduced. In this situation, it can be said you have LESS ENGINE BRAKING. However, if your riding “style” makes this an issue, a slipper clutch may be a better alternative than a lightened flywheel; at least that’s what the factory racers think. A lightened flywheel is like a poor man’s slipper clutch in this situation.

Conversely, a heavier flywheel will provide more protection for the engine being over-revved in a ham-fisted downshift.

The ability of an engine with a lightened flywheel to SPIN-DOWN more quickly is often pointed-to as a benefit if you want the revs to die as fast as possible when you lift the throttle for a corner. In this situation, it can be said you have MORE ENGINE BRAKING. Under normal street riding conditions we tend to prefer less engine braking so we tolerate a less efficient situation where the motor then has to work harder to put more momentum into the flywheel. When racing, you don’t care about storing momentum, you just want to get around the track as fast as possible.

This enhanced ability of the engine to spin-up and spin-down also makes it less critical to match engine and drive train rpm for smoother shifts. That is, the heavier the flywheel the longer the engine rpm will hang between shifts requiring a need to release the clutch more slowly to avoid lurching forward when quickly engaging the next higher gear.

So, the purpose of the flywheel is to store momentum, reduce vibration and smooth out the loads transmitted to the drive train. It takes energy to first store this momentum, so if the flywheel is lighter it takes less energy and it accelerates up to speed faster. There is an opposite effect when you lift off the throttle and momentum is given up, so the revs drop slower for a heavier flywheel.

Because the engine will spin-up more quickly with a lighter flywheel, when you loose traction, modulating the throttle (especially in the rain) will be more difficult. Especially if your throttle position sensor, idle and CO are not adjusted properly. A light flywheel seem to exacerbate a poorly tuned fuel injection system. If you make 100 horsepower it’s less of a issue. Make 130 hp and it will matter a whole lot more.

The amount of weight removed from the flywheel and inner hub is proportional to this effect, although if you remove most of the weight from the outer rim area, the effect is stronger. Different after-market manufacturers of flywheels offer different weights and geometry. If lightweight is good, ultra-lightweight is better - just doesn’t apply here. Too light a flywheel can make the bike a handful to ride so a two pound flywheel for the street seems to be a good compromise to preserve some ride-ability.

A cold engine runs rough until there’s enough heat to vaporize the fuel, so until then, a lighter flywheel will be less effective in preventing stalls, especially pulling away from a uphill stop. You’ll need to rev the engine a little higher to compensate and you may find it’s a little ornery when running at light loads (3,500 rpm) in the lower gears around town. Often, your idle speed will need to be raised to around 1,300 rpm to help minimize stalling.

You’ll also risk sprag clutch wear or damage. Ducati mechanics see a lot of worn-out starter clutches when there is a very light flywheel attached. Why? Often lighter flywheels seem to let the engine kick-back much harder during start-ups and shut-downs, which causes starter clutch damage.

With all that said, you’ll find plenty of owners that will praise the effects of a lighter flywheel on their bike - but perhaps one that’s different than yours. Not every bike will respond well to a light flywheel, mainly because the flywheel is just part of the overall rotational inertia of the crankshaft, connecting rods and alternator.

So, if you have an old alternator SP/SPS with the lighter crankshaft and titanium connecting rods, the effect of removing 1kg from the end of the crank will be very noticeable, because the total mass is much lower to begin with. A non-SP or 2-valve bike has more crank/rod weight, so the effect is less pronounced.

For example, on a 916, or any model with a single pick-up and older version alternator, you can just remove the flywheel weight and run the starter clutch hub. Inexpensive, and makes them quite responsive.

However, a late-alternator bike with the heavier full-counterweight crankshaft and standard rods has significantly more weight in the alternator assembly and machining the same 1kg from the flywheel will have less of a negative effect, again - due to the higher initial combined mass of the set up.


Lightweight Wheels Instead

Lightweight wheels don't have the stalling and drivability drawbacks of a lighter flywheel. Also, since the wheels have a much greater rotational inertia than a flywheel, weight reduction here results in a much greater improvement in acceleration (and braking) with an added benefit of reduced gyroscopic forces for improved handling. Lighter front rotors have a similar benefit. There’s even a significant difference in tire weights between brands to consider.

Most of what you said made my head hurt.   :P

This caught my attention though... ;)

QuoteOf course every 0.3% helps a racebike. When you reduce weight you’ll get faster acceleration, and faster lap times - IF - you can modulate your wheel spin driving out of corners. Factory racebikes make so much power, for example, that transmitting the power to the road effectively becomes the limiting factor - so heavier flywheels actually become a benefit. Fear the high-side.

Never let it be said that Shazaam! is a man of few words.  ;D

Welcome to the asylum.  [beer]

+1 Shazaam!,

Thanks for explaining the physics in terms we all understand..    [thumbsup]

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
This is a known problem and an issue that you should consider before you add a lightweight flywheels to a Ducati. Ducati sees a lot of worn-out starter clutches when there is a very light flywheel attached. Why? Often lighter flywheels seem to let the engine kick-back much harder during start-ups and shut-downs, which causes starter clutch damage.

Why is there any kick-back at all in this system?  My 2003 Triumph Speed Triple has gone through 100x the abuse I've put my 1098 through and its starter is just fine and almost always starts the bike on the 1st or second try unless the battery is low.  Seems to me this 'kick-back' issue is Ducati's fault since as you noted, it does it with the stock flywheel.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
Why You Have a Flywheel

A lightened flywheel is one modification to a STREET bike that will have more negative than positive effects. I left mine stock. Here’s why.

An engine makes the least torque at idle and low rpm, especially when cold (when there are more misfires.) So when you release your clutch a little too fast, the engine torque is too small to overcome the bike's inertia, and it stalls. If you have a flywheel, the stored momentum augments the engine's torque allowing you to use a lower rpm starting-off. Without a flywheel you'd need a higher idle speed, or constantly need to start-off at a higher rpm in order to raise the engine torque output enough to avoid stalling the engine.

I had no problems taking off and didn't seem to have to rev the bike much higher than with the stock flywheel to get it to take off from a stop.  HOWEVER, it DID make the entire bike ride smoother at low RPMs and there was virtually zero chugging (mirrors flapping at 3000-3500rpm) compared to stock.  Also, the bike idle'd just fine at the stock idle.  It did stall a few times, but that could have been more related to the fact that the bike had been sitting in the shop waiting to get worked on for over a month or it could have been the flywheel.  No way to know for certain since the sprag crapped out after I shifted into first at a stoplight with my hand off the clutch.  That action probably would have destroyed the sprag on this bike even with the stock flywheel, but DNA found an excuse to deny my claim for the full repair.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
As you ride at lower rpm in traffic, you are constantly changing between acceleration and deceleration. Engine torque levels are still fairly low at these speeds, so slack in the drive train needs to be smoothed-out with a flywheel. Otherwise, on-off throttle transitions have a jerky effect, giving a less comfortable ride and causing you to use smaller throttle inputs (which is not always easy to do.)  At higher speeds a flywheel slows the rate at which an engine rpm changes, so cracking the throttle open or closed results in a smoother transition in torque being applied to the drive train and tires. Again, without a flywheel more careful throttle transitions are needed. The key to faster track times is reduced wheel spin so a light flywheel works against you by making it more difficult to modulate wheel spin, even though it helps lap times by producing more acceleration in the straights.

Again, I found the exact opposite to be true with the lighter flywheel for the 3 days I was riding with it.  Lower RPMs were exceptionally smooth compared to stock and throttle inputs were actually EASIER to manage since the entire bike was running smoother.  Also, since the engine was able to spin up and down faster, I was able to click through gears much more smoothly (not that I don't already blip the throttle on downshifts).  Handling was also seemingly improved over stock.  The bike felt a bit more lively and flickable than it already was.

The bit about higher speeds is correct, but I'm not using this bike for the track much and I'm already very conscious of my throttle and braking inputs and the overall 'behavior' of the bike while riding.  If the rear starts to slide, I adjust.  I'm not the least bit hamfisted and looking to race fools in the canyons on public roads, so high-siding isn't really a concern.  If I did a trackday on this bike, I'm sure I would gradually increase my pace rather than trying to WOT out of corners at every exit like a jackass.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
And, when you miss a shift you’ll be glad you have one ...

I don't get this statement.  If you miss a shift, the RPMs would flick up or down to where they need to be for the gear with the lightweight flywheel.  I'd be more worried about missing a shift with the stock flywheel as the increased chance of wheel hop on downshifts could be really scary mid-corner if you're 'tarding it up' and just flogging the throttle and shifter mid-turn.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
Lightweight Flywheel - Pros and Cons

The weight of the stock flywheel is derived by Ducati test riders to provide an overall balance between performance and smooth drive train behavior. That's why Ducati selected the flywheel weight that they did. Did you think that they meant to purposely cripple the bike's performance by using a too-heavy flywheel?

When you remove weight from the flywheel (and to a lesser degree, from the clutch) the effect on the engine’s ability to more quickly spin-up is indistinguishable from increasing your engine’s torque (and consequently horsepower) output.

But only in neutral. In any other gear, there’s little benefit at all.

Again, wrong.  The acceleration difference was notable.  I wasn't looking for a power increase, just better usability of the available power for my riding style.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
Obviously, your bike’s ability to accelerate faster through the gears is enhanced by reducing the overall weight of the bike as well as the inertia of rotating components. The crankshaft, pistons and connecting rods, transmission gears, drive chain and sprockets, wheels and tires, clutch and flywheel are all candidates.

However, the overall weight of the bike and rider completely overwhelms any reduction of rotational inertia produced by a lighter flywheel. A two pound lighter flywheel on a 600 pound bike-plus-rider will accelerate only 0.3% faster. F=ma.

I think your math is a bit off, but regardless, the changes were quite notable.  Have you tried a lightweight flywheel on a 1098?  Also, I did not notice a huge change to engine braking.  I think the rest of the motor's weight and compression was a factor in retaining a good amount of engine braking on the bike.  You'd be pretty hard-pressed to take all of the engine braking away from a big-displacement twin.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
Conversely, a heavier flywheel will provide more protection for the engine being over-revved in a ham-fisted downshift.

This is why we have rev-limiters and you shouldn't be over-revving your bike even with the stock flywheel anyway.  Again, I'm not a ham-fisted rider so this doesn't really apply.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
So, the purpose of the flywheel is to store momentum, reduce vibration and smooth out the loads transmitted to the drive train. It takes energy to first store this momentum, so if the flywheel is lighter it takes less energy and it accelerates up to speed faster. There is an opposite effect when you lift off the throttle and momentum is given up, so the revs drop slower for a heavier flywheel.

I found the exact opposite in my experience.  The engine seemed to run smoother at idle and it definitely ran smoother through the entire rev range on the road.  Heavy flywheels are put on cars and motorcycles to make the powerband more manageable for the average rider/driver. 

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
Because the engine will spin-up more quickly with a lighter flywheel, when you loose traction, modulating the throttle (especially in the rain) will be more difficult. Especially if your throttle position sensor, idle and CO are not adjusted properly. A light flywheel seem to exacerbate a poorly tuned fuel injection system. If you make 100 horsepower it’s less of a issue. Make 130 hp and it will matter a whole lot more.

Where did you copy and paste this from?  The 1098 is known to have 140+rwhp.  Also, I've ridden the 1098 in pissing down rain on a trip from Dallas, TX to Toledo, OH and back and it wasn't nearly as horrible as this last statement makes it out to be.  I've also ridden my Speed Triple, a Honda Valkyrie, and several other bikes in rain with no major issues.  You just can't assume you have any traction and you ride accordingly.  Try to drag a knee in the rain and you're gonna die.  Duh.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
You’ll also risk sprag clutch wear or damage. Ducati mechanics see a lot of worn-out starter clutches when there is a very light flywheel attached. Why? Often lighter flywheels seem to let the engine kick-back much harder during start-ups and shut-downs, which causes starter clutch damage.

I'm still waiting for better evidence than the half-ass explanation I was given.  Does Ducati have documented evidence which shows empirically that lightweight flywheels destroy starter sprags?  Do they have proof their starting system design isn't flawed to begin with and a lightweight flywheel only makes this much more obvious?...

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
So, if you have an old alternator SP/SPS with the lighter crankshaft and titanium connecting rods, the effect of removing 1kg from the end of the crank will be very noticeable, because the total mass is much lower to begin with. A non-SP or 2-valve bike has more crank/rod weight, so the effect is less pronounced.

Again, where did you cut'n'paste this from?  We're talking about a 1098, not an older 2-valve bike.  The last bit about lightweight wheels has nothing to do with the topic at hand; "Will a lightweight flywheel damage a starter sprag?"

"Conversely, a heavier flywheel will provide more protection for the engine being over-revved in a ham-fisted downshift."

"This is why we have rev-limiters and you shouldn't be over-revving your bike even with the stock flywheel anyway.  Again, I'm not a ham-fisted rider so this doesn't really apply."

You miss the point,  down shift one or more ratios than intended and the rear wheel will overdrive the engine, the rev limiter would have no effect.

BTW I have the DP lightweight flywheel fitted to my S4R and can only report positive results over the stock item.

Having read many of Shazzam's dissertations over the years, if any cutting and pasting is going on it would be from his posts, he is a well respected engineer in Ducati circles and is privy to information not readily accessible to the rest of us.

Many points in his post are illustrative and serve to further the understanding of the operation and the factors affecting it.

I've been watching this thread with interest. I think the physics of how a flywheel works is pretty easy to understand (as well as any other rotating engine part). I wouldn't recommend one for a bike that is used for touring or commuter duty, but they have a big advantage in a sport riding arena. They let the motor spin up and down quicker and give the rider a better throttle response and a better "connection" to the motor. Most of us aren't nearly as good of riders that we think we are and anytime you give the rider more control or adjustability, it can lead to worse results as well as better ones.
Overall, I think a lighter flywheel makes a big improvement (I include one on every bike) and haven't seen any evidence of sprag problems or any form of "kick back". It isn't, nor should be considered, a substitute for a slipper clutch.

QuoteHaving read many of Shazzam's dissertations over the years, if any cutting and pasting is going on it would be from his posts, he is a well respected engineer in Ducati circles and is privy to information not readily accessible to the rest of us.

I think the OP is probably justifiably frustrated with his starter sprag problem and some of it's understandably showing through in his post.  This is a very interesting and educational thread, and I hope we can overlook a few transgressions and keep it from getting personal.

It would also be interesting to get Nichol's Mfg view on some of this, especially the sprag clutch issue.  If I have some time later today I'll email them.

+1 I noticed that my sprag lay in pieces after the engine being stipped by one of the junior guys at the shop.
Guess we will be having a conversation over it when the bill is produced.

In reference to the original post: No offence intended, honest question, how did you knock it into gear at a traffic light? Been riding for nearly 40 years, dirt bikes and street bikes, never done that, and don't think I know anyone who has, and when I started riding there was no standard control layout. Some were left shift, some right, some 5 up, some 1 up 4 down, etc. Is it that common to happen?

Quote from: JetTest on December 23, 2008, 11:03:17 AM
In reference to the original post: No offence intended, honest question, how did you knock it into gear at a traffic light? Been riding for nearly 40 years, dirt bikes and street bikes, never done that, and don't think I know anyone who has, and when I started riding there was no standard control layout. Some were left shift, some right, some 5 up, some 1 up 4 down, etc. Is it that common to happen?

I was sitting at the light and went to put my foot down and my pant-leg caught the shifter peg.  Total stupid accident.  You've never accidentally bumped the shifter into gear at a stop in 40 years of riding?  Maybe you've just been really lucky and developed exceptionally good habits?  I've seen plenty of people have their bikes click into gear at stops, while coasting in neutral to a stop (thinking the bike couldn't ever just be in a false neutral...), go over a bump in neutral and have their bike click into gear (my wife somehow managed this one in a parking lot).  I think I've accidentally clicked into gear maybe 5 times or so across the last 20ish years of riding, maybe more, but its still pretty rare.  That doesn't mean it should completely frag a starter sprag though.  This is the first bike I've been on which has had anything starter-related go out.  It doesn't help that Ducati has multiple warranty service notices on various parts of the early 1098 starting system.  I've got a nice stack of paper to take into whatever dealership I end up with to make damn sure everything is up to date and operating properly.

I meant no offense to Shazaam when I mentioned cut'n'paste.  I just felt some of the points could have been better applied to the 1098 and the topic at hand.  In general, most of those points fit, especially for cars not designed for a lightweight flywheel.  I'm just annoyed at the shop who did the install (told me the lightweight flywheel would cause no damage then flip-flopped when DNA said no) and DNA because the law requires they provide proof the flywheel caused the damage, but I don't have the time or money right now to start a he-said-she-said small claims court filing from halfway across the country and end up putting more into that than I've already spent on the install/uninstall/repair.

Oddly enough, now the bike seems to be starting normally although the start-up is still pretty clicky/noisy compared to what I remember before this whole bs situation.  Hopefully things will stay right. 

So here is another question;  How many of you would renew or buy an extended Ducati warranty if you'd gone through this situation?  Mine runs out in June.

My bike is never in neutral if it is moving, only stopped and I never coast, to a stop or otherwise. You have less control and it allows more false neutrals. When stopped, my left foot stays on the peg incase I have to move if a car approaching from behind appears to not be stopping in time. That aside, I agree you have every reason to be pissed at the shop that gave you terrible service and stole your flywheel, aswell as DNA for not honoring your warranty ans supporting their product.

QuoteLaws are fine and dandy but unless you yourself are a lawyer, its going to cost you more money and time to settle the matter legally than to just explore your options and settle accordingly. Experiences with DNA (Ducati North America) have gone both ways so but most of the time they are reasonable.

1) Another Dealer
2) Appeal to DNA directly
3) Get a lawyer to write a letter to the dealership
4) Become a greasemonkey and do it yourself.

Although I will never own a 1098 with a light flywheel I am interested in Ducatis response to these warranty issues. Did you communicate directly with DNA as suggested earlier. If so what was their response to you. It seems from other posts DNA response is sometimes more favorable than the dealer.

I sent an email and attempted to call several times but didn't get through to anyone important.  The few 'friend of a friend' connections I had were for the wrong region (east coast, and I was in Texas at the time).  If I run into another situation like this in the future, now that I'm no longer hopping around dealing with grad school and career moves, I'll be doing everything I can to get my voice heard by DNA or any other manufacturers I might run into BS with. 

Every time I take the bike out, I'm reminded why I fell in love with it in the first place.  Its just frustrating when I see my money burning off for nothing.  Not that I have a ton of cash having just finished grad school and moved to southern California (living expenses...  $$$$$). 

I'm thinking once the warranty runs out, I'll be doing all work myself unless it is motor-related.  I can't afford to buy broken engine parts if I don't assemble something juuuuust right, so I'll leave that to the pros.  I also shudder to think of how many specialty tools I'd have to buy to work on that motor.  There seem to be plenty of competent Ducati mechanics around here, so I should be good on that front.  I've done the rest myself on multiple bikes including a custom GSXR front end swap on my Triumph. 

QuoteIMHO the subsequent failure was attributable to the installation not the effect of the flywheel itself.

And, to take it one step further, I wonder if the reason they stole his Nichols flywheel was to hide the evidence?
I know it's pure conjecture but it just rubs me wrong that they didn't return the flywheel.

I'll put the lightest flywheel I can stand to drive with on anything with a manual box, and continue to reap the benefits.   The small amount of driveability annoyance can easily be "ridden" around with technique (IE, just a smidge more trottle to drive away from a light).  My 900ss liked it, my 999 REALLY like it, and the S4RT seemed to like the mod even more, with respect to the bike feeling a bit more nimble (reduced gyro). 

The more problems I run into with Ducati service/dealerships, and FACTORY manual having bogus/wrong info in it, and reading crap like this.....well lets say I'm not sure my next 15K motorcycle purchase will be with ducati.

The the OP.  Man, I hope you get this sorted out.  You were charged for installing a part, charged for fixing the shop's screw up, and then your part was stolen, and the MFG denied to help you.  F that.

This supports my standard philosophy: buy used - do the work yourself or thru a small independent shop.

Shazaam,  Thanks for taking the time to write all this out for us.   I have a few comments.  I should start out by saying that I don't have a lightened flywheel, although it's on my list.  I'm interested in this topic out of personal curiosity.

Quote from: Shazaam! on December 22, 2008, 04:12:04 PM
This is a known problem and an issue that you should consider before you add a lightweight flywheels to a Ducati. Ducati sees a lot of worn-out starter clutches when there is a very light flywheel attached. Why? Often lighter flywheels seem to let the engine kick-back much harder during start-ups and shut-downs, which causes starter clutch damage.

I talked to an independent tech with lots of lightened flywheel experience.  He agrees that he sees a lot of worn out starter clutches with light flywheels.  He also says he sees a lot of worn out starter clutches with stock flywheels.   His opinion is that there is  no correlation whatsoever between flywheel weight and starter sprag failure.   However, he doesn't have any written records or statistics to back this up.   Can you provide any actual numbers for sprag clutch failures with lightened flywheels vs stock flywheels?  Without actual documented numbers what you are presenting as a fact is still just one more subjective personal opinion.

QuoteAs you ride at lower rpm in traffic, you are constantly changing between acceleration and deceleration. Engine torque levels are still fairly low at these speeds, so slack in the drive train needs to be smoothed-out with a flywheel. Otherwise, on-off throttle transitions have a jerky effect, giving a less comfortable ride and causing you to use smaller throttle inputs (which is not always easy to do.)

This, and some of your other discussion points make perfect sense - on paper.  However, in the real world where most of us live some of the time, everyone I've talked to or read a post from concerning their lightened flywheel have been downright gleeful about the performance, theoretical drawbacks and all.

QuoteBut only in neutral. In any other gear, there’s little benefit at all. However, the overall weight of the bike and rider completely overwhelms any reduction of rotational inertia produced by a lighter flywheel. A two pound lighter flywheel on a 600 pound bike-plus-rider will accelerate only 0.3% faster. F=ma.

It looks to me like F=ma is being misapplied here.  Also, I think the reduction in weight from stock to Nichols is closer to 4 pounds than 2 pounds.  And it isn't just the amount of weight removed, it's where on the flywheel the weight is removed from and its effect on the moment of inertia that counts.

F=ma generally applies to a non-rotating mass being  accelerated in a linear fashion, a rider's beerbelly being a good example.  For a rotating flywheel, I think the correct equation is something like F= Ia where I is the moment of Inertia and a is the angular acceleration, completely different animal from linear acceleration.  The energy stored in a rotating flywheel (and this energy has been"stolen" from the energy that would be applied to the rear wheel)  is a function of the square of the angular velocity of the wheel.  If you've considered all this in your 0.3% calculation you have my apology in advance.

QuoteYou’ll also risk sprag clutch wear or damage. Ducati mechanics see a lot of worn-out starter clutches when there is a very light flywheel attached. Why? Often lighter flywheels seem to let the engine kick-back much harder during start-ups and shut-downs, which causes starter clutch damage.

Again, before this can be accepted as fact rather than personal opinion we need documented numbers on the sprag failures on light flywheels vs stock flywheels, please.  I'm not saying that it's not true, I just want to see data.

QuoteLightweight Wheels Instead

Lightweight wheels don't have the stalling and drivability drawbacks of a lighter flywheel. Also, since the wheels have a much greater rotational inertia than a flywheel, weight reduction here results in a much greater improvement in acceleration (and braking) with an added benefit of reduced gyroscopic forces for improved handling. Lighter front rotors have a similar benefit. There’s even a significant difference in tire weights between brands to consider.

Since as mentioned above, the momentum is a function of the angular velocity squared, I'd like to see the difference in energy stored in a stock flywheel rotating at say 6,000 RPM vs a stock wheel/tire at say 1400 RPM at 100mph or so (also need to consider that we have two sets of wheels/tires).   Not saying it would be greater but it would be interesting to see actual numbers.  

I think that most of my  point of my above comments is that without either documented empirical test results and/or valid numbers punched into Mr.  Newton's equations, this  discussion, mine included, is all just personal opinion without a base in facts.  Again, thanks for taking the time and effort to write your long post and I hope none of this comes across as personal criticism. 

+1 on the above post with regard to rotational mass.  If you've ever done the 'spinning bicycle wheel on an axle' twist in a physics experiment, you know increased speed and/or weight makes the wheel harder to turn (centrifugal force stabilizes the wheel?  I think centripetal force was the theoretical 'pushing back' force, right?).

Granted, installing lightweight wheels is a lot safer, but lightweight wheels also cost around $2000+ and I wouldn't go with anything less than BST's carbon fiber street wheels on my 1098.  That won't be happening anytime soon, and I'll DEFINITELY be buying a No-Mar tire changer before buying those wheels so I can be damn sure no one screws up my wheels but me (and thats pretty hard to do with a No-Mar).

On the other hand, while installing a lightweight flywheel might be cheaper, it could actually end up costing a ton more if you misplace your trust in a shop to do the work and something goes wrong.  Lesson learned.

I didn't read 100% of Shazzam's post, but I noticed some contradictions with literature I have read as well.

Lightened rotating parts should equal faster lap times all other things equal - note the latest crop of 800cc gp bikes - faster corners in part due to less gyroscopic effects of the engine.

Also, the big bang traction theory has been challenged by the concept of power feedback.  If the engine is controlling the speed of the bike mainly due to throttle inputs, then the rider has a better feel, more confidence and control.  If the speed of the bike is being controlled to a greater extent with the inertia of rotating engine parts and not throttle input (like a balanced I4 engine), then the rider has less feel, slower times.  Note the newest Yamaha M1 and R1, not to mention the V4 bikes in gp have out of balance cranks.

I will likely never even try a light flywheel, so I have no FHE, but I am a mechanical engineer, and the idea of lower mass = faster is the only logic that lines up with physics.

mitt

Quote from: Norm on December 24, 2008, 08:25:19 AM
This supports my standard philosophy: buy used - do the work yourself or thru a small independent shop.

Norm, I'm with you 100% on this and that's exactly what I do.  None of my bikes have ever seen the inside of a dealership or shop of any kind.   The problem seems to be that there are riders out there who like to buy new (which is absolutely fine) and don't have the interest or time to do their own work (which is also absolutelly fine).   They "should" be able to take their bikes to their dealer and get quality work done at a fair price. Unfortunately in many cases they end up getting screwed.

In my biased opinion part of this problem is the decline of the local bike dealer who became  a dealer because he was a rider  and loved the sport.  He sold and worked on bikes all week and then went racing on weekends.  Almost all of the dealers I see today are based on the Home Depot style of marketing and seem to be owned by investors who just want to suck money off the top.

Absolutly, there is a large Yamaha delaer near me, salesmen were suits and none of them know how to ride a motorcycle. My conversation with them lasted 60 seconds.