15/41 works really well on my carbie 900.

Your primary and trans gearing is slightly different so that might not work for you.

I would think 14/42 would be kind of buzzy on the highway.

Quote from: ducpainter on January 17, 2014, 05:03:14 AM
15/41 works really well on my carbie 900.

Your primary and trans gearing is slightly different so that might not work for you.

I would think 14/42 would be kind of buzzy on the highway.

What was your carbie 900 stock?

Also: buzzy?

Quote from: 1.21GW on January 17, 2014, 06:57:40 AM
What was your carbie 900 stock?

Also: buzzy?

It was 15/39.

Revving too high at highway speeds resulting in too much vibration for comfort over a long distance on the slab.

my original was 15/48 now running 14/48 . . . love it in the city, not for long runs . . .

Quote from: ducpainter on January 17, 2014, 05:03:14 AM
15/41 works really well on my carbie 900.

Did some more sprocket reading.  According to Bikey Boy Brad's chart (http://www.bikeboy.org/ducgearing.html) I'm at 4712rpm in 6th at 70 mph, assuming I am stock (15/39---I have to check and make sure PO didn't change), which similar to your 15/41 @ 4806, DP.

My issue isn't really low gear pull in city/suburbs.  In fact, I don't really have any issues other than the fact that 5th is kinda useless for my riding: I'm either in 4th (for pull) or 6th (for MPG and relative smoothness) on highway, 1st-3rd everywhere else.

But seeing as I've ridden very few bikes in my life, I wanted to consider changing something for the learning experience if not performance upgrade/change.  I can always go back.  That said, I think I'm fine with my ratio.

Thanks to input here and on copious older threads.   I feel 0.00001% smarter! 

Maybe ride a similar bike with shorter gearing when you won't need skis to do that? 

On the newer Monsters 14T is very popular as it's a cheap fix for VERY tall gearing. On my 796, 6th was almost useless under 80 MPH, and with stock fueling, the bike is pretty rough under 4,000 RPM. No idea how this applies to an older 900 like yours.

Some bikes cry for it and some don't (or can handle the tall stock gearing). Out of eight Ducatis I've owned, two cried for it.

And my point was... As you are changing everything, better to go with 15 up front and a compatible increase in the rear which roughly equals a 14T up front. In theory a 15 will wear the chain less... YMMV

Quote from: 1.21GW on January 21, 2014, 07:20:08 PM
Did some more sprocket reading.  According to Bikey Boy Brad's chart (http://www.bikeboy.org/ducgearing.html) I'm at 4712rpm in 6th at 70 mph, assuming I am stock (15/39---I have to check and make sure PO didn't change), which similar to your 15/41 @ 4806, DP.

My issue isn't really low gear pull in city/suburbs.  In fact, I don't really have any issues other than the fact that 5th is kinda useless for my riding: I'm either in 4th (for pull) or 6th (for MPG and relative smoothness) on highway, 1st-3rd everywhere else.

But seeing as I've ridden very few bikes in my life, I wanted to consider changing something for the learning experience if not performance upgrade/change.  I can always go back.  That said, I think I'm fine with my ratio.

Thanks to input here and on copious older threads.   I feel 0.00001% smarter! 

Thanks for the link. Hadn't seen that. Although I don't think my 15/43 S4Rs is doing 4647rpm @ 70mph. Either that or the tacho is a few hundred off.

Another interesting chart on that page is the small table that gives the percentages between gears. On the standard gearbox, 5th to 6th is 11 per cent.

That is roughly equivalent to going from your 15/39 sprocket set to a 14/40 or 14/41.

So ... if you want to know how your bike would feel in sixth with that change, just try riding it around in fifth for a while. 


(BTW, 14/42 is an even division, and so likely to attract more rapid wear, or so I've read. For that reason, I doubt it's a popular choice. I wonder whether the popular mod you are thinking of is just to go up on the rear only, to 15/42.)

Quote from: 1.21GW on January 21, 2014, 07:20:08 PM
Did some more sprocket reading.  According to Bikey Boy Brad's chart (http://www.bikeboy.org/ducgearing.html) I'm at 4712rpm in 6th at 70 mph, assuming I am stock (15/39---I have to check and make sure PO didn't change), which similar to your 15/41 @ 4806, DP.

My issue isn't really low gear pull in city/suburbs.  In fact, I don't really have any issues other than the fact that 5th is kinda useless for my riding: I'm either in 4th (for pull) or 6th (for MPG and relative smoothness) on highway, 1st-3rd everywhere else.

But seeing as I've ridden very few bikes in my life, I wanted to consider changing something for the learning experience if not performance upgrade/change.  I can always go back.  That said, I think I'm fine with my ratio.

Thanks to input here and on copious older threads.   I feel 0.00001% smarter! 

If what you currently have works for you, don't change it just to follow the herd.

IMO, only having to drop one gear to pass would be handy but you would have higher rpms in top gear, and you might not like that.

I want to keep my setup the way it is, so I just checked my bike and I actually have 14/38.  Guess the PO made a change.  (Not a common ratio, but I double- and triple-checked it.  I am assuming that it is the teeth (spikes) on the sprocket I am supposed to be counting.)

Anyway, I see that 14/38 and 15/41 are roughly the same RPM @ 70 according to Bikeboy's page.  I have two questions now:

1. I am inclined to do 15/41 because I've read some places that the 14 front can put more stress on the chain or create swingarm wear due to tight angle.  Opinions on this?

2. However, my chain (DID 520 VX2) is ~1 yr old and has 2000 miles, so I'd like to keep it is possible.  Am I correct to assume the move from 14/38 to 15/41 would require a new chain?

Quote from: 1.21GW on January 25, 2014, 08:10:33 AM
I want to keep my setup the way it is, so I just checked my bike and I actually have 14/38.  Guess the PO made a change.  (Not a common ratio, but I double- and triple-checked it.  I am assuming that it is the teeth (spikes) on the sprocket I am supposed to be counting.)

Yes, it is the teeth (spikes) that you are supposed to be counting.

Might be worth a quadruple check. 14/38 suggests the PO went down one on the front, decided that was too low and so corrected a bit by going down a single tooth on the rear. Possible, but doesn't sound very likely.

Compared with ... 14/39. Stereotypical Duc gearing change: one down on the front.

Not sure on the chain but I imagine that yes, you would need to get a longer chain or add a few links to the chain you have.

BTW: Another advantage of going to bigger sprockets is extra chain clearance near the swingarm pivot area. If you really are running 14/38, that clearance must be fairly tight, I'd have thought.

Quote from: Moronic on January 26, 2014, 03:04:44 AM
Might be worth a quadruple check. 14/38 suggests the PO went down one on the front, decided that was too low and so corrected a bit by going down a single tooth on the rear. Possible, but doesn't sound very likely.

Yeah, thought the same thing.  Doesn't matter, though, since it's coming off.  I'm going to order 15/41.

Quote from: 1.21GW on January 25, 2014, 08:10:33 AM
I want to keep my setup the way it is, so I just checked my bike and I actually have 14/38.  Guess the PO made a change.  (Not a common ratio, but I double- and triple-checked it.  I am assuming that it is the teeth (spikes) on the sprocket I am supposed to be counting.)

Anyway, I see that 14/38 and 15/41 are roughly the same RPM @ 70 according to Bikeboy's page.  I have two questions now:

1. I am inclined to do 15/41 because I've read some places that the 14 front can put more stress on the chain or create swingarm wear due to tight angle.  Opinions on this?

2. However, my chain (DID 520 VX2) is ~1 yr old and has 2000 miles, so I'd like to keep it is possible.  Am I correct to assume the move from 14/38 to 15/41 would require a new chain?

Hey, as of right now, I installed on a customer's M620 5 speed a 15/38 combination, because he needs to travel long distances, he says that he loves it, but, would like to have the oomp of the bike when he brought it to me and keep the fuel economy, so, I told him I could go 15/41 but, no more on the rear, so, yes, if you have 14/38, go 15 front and enjoy the chain for an extra 8 000 miles at least.

Personally I don't like to add new links to used chains. but yes, 15/38 is gonna work but,, you will loose a lot of driveability on low RPMs . . .

Ok, just about ready to order.  Going to get a new chain and do 15/41.

Question: Need to get a chain breaker/riveter---anyone have a preferred recommendation?

http://ca-cycleworks.com/products/garage-accessories/mp08-0470  will be fine.  Before breaking the chain grind off the head of the rivet.  You can also buy your chain and sprockets from our friend at Ca-Cycleworks.  Quick turn around and they know what fits

Thanks, Howie.  Will order shortly. 

Wheels and rear sprocket ordered from Motowheels.   Ordering chain breaker, chain, and front sprocket from Ca-Cycleworks.  Also ordered a Shorai battery and timing belts from Monsterparts, so I'm really spreading the sponsor love this month.



I'm sure I will be back on this thread in a month or two with install questions...