Bike:  1999 M900s

Symptoms: A couple of months ago, Stillie was riding my bike to work and got about a mile and a half from the house.  It hiccuped once and then cut off almost as if out of gas (which he knew was untrue).  Getting it home, it will run for as long as we're dumping fuel or starter fluid into the intake (good on air and spark).  Replaced the fuel filter, which was in need of replacing.  Still doesn't run.  Fuel is getting to the carbs and the bowls do refill when emptied.  Inspected the carbs and nothing seems gooey beyond the usual amount of residue.  The only thing amiss was a cracked hose. 

So here's with the hose identification problem.  The hose comes from the little plastic triangular breather-ish-looking box that is mounted on the outside of the frame.  The hose is wrapped in a spring to keep it from kinking.  It has a filter in the line.  It goes to a point mounted in between the carbs.  What is it?  I can snap a pic tomorrow.  This hose had a small crack in it that had light debris along the thickness of the hose, indicating that we didn't cause the crack on disassembly. 

So the mystery is that it looks like fuel is getting to the carbs and should go through the carbs, and the only thing amiss was this hose that was cracked.  What is that hose and would the crack cause it not to run?  What else should I inspect?

The hose is a carb diaphragm vent hose.

I don't think that's your problem.

Quote from: ducpainter on August 07, 2008, 07:05:12 PM
The hose is a carb diaphragm vent hose.

I don't think that's your problem.

Vacuum issue somewhere/somehow?

Possibly the vacuum line to your fuel pump is compromised, or your fuel pump has expired.

Quote from: Speeddog on August 07, 2008, 10:23:07 PM
Possibly the vacuum line to your fuel pump is compromised, or your fuel pump has expired.

That's my thought as well.

The hose that goes to the little plastic pod just has to sit in idle air. So make sure you put it back. If the hose is slightly cracked, it won't actually matter much, but you might as well replace it.

As said before, I'd check into your fuel pump.

If you remove the hose between the pump and carbs gas flows freely from the pump. We discovered fuel in the carbs last night after a quick tear down. Tonight we plan on rebuilding the carbs but I don't think they are at fault. Kind of at a loss here. 

Doesn't really make much sense...

If the bike has a vacuum operated petcock I'm wondering if the fuel flows when the bike isn't running and was being diverted or shut off when it was.

Even then...it should at least start.

Shooting in the dark here....

Perhaps the fuel pump is jacked, such that with vacuum signal it's shutting off the fuel supply.
I've not heard of this failure mode, but.....
Try running it with the vacuum line to the fuel pump unhooked and plugged so that it's not an air leak to the manifold.

As DP said, maybe the vacuum petcock is not operating correctly.

Very odd.

Ok, so here's the drama as it unfolded tonight...

We brought her to a friend's place who is way more knowledgeable than either of us.  He's an SV guy but we like him anyway.  He teaches us about carburetion in exchange for Guinness.  How could we not like the guy?

We finished cleaning out the carbs.  We blew air through everything and reassembled the rest of the bike most of the way, just enough to test to see if it would run.  Fired right up.  But wait, there's more.  It sounded very wrong to me.  Stillie looked at me puzzled, "Isn't that how it's supposed to sound?"  It sounded strangely.... thumper-ish.  ACK!!!  Only one cylinder firing!!!  Now we have created an electrical problem and it's time to find it.  Somehow one of the connectors on the bottom of the coil for the vertical cylinder got bumped off, so after a few dry chuckles and embarrassed coughs, it all came together.  Both cylinders roared to life. 

YAYAYAYAY!!!!!!

Stillie geared up and off we went.  I was so relieved that we fixed the problem, but perplexed at what it was.  It really didn't sound like it was a carb issue because they both died all of a sudden.  Weird.

We got down the road a bit and he started to pull over and then I saw it.  She was so mad that we hadn't fixed the problem that she shot HUGE flames out the ass end.  And then she died the same death she did before.  She'd start and idle, but she wouldn't take any throttle.  Well poo. 

So now we do know much more about the problem.  Those in the fuel pump camp are probably on the right track more than we were.  Yes, the carbs were an issue, but only a secondary problem caused by my delay in fixing it. 

What we do know is that the bowls are for some reason being drained faster than they can be filled.  So it's either a vacuum issue with the pump demand or the pump is in the process of giving up the ghost.  I'll keep everyone posted.  And thank all you fuel pump nay-sayers for making me feel like an ass for doubting you! 

And are there any other gems of wisdom or alternate theories anyone cares to offer?

Pump rebuild info here:
http://ducatimonsterforum.org/index.php?topic=4274.msg65213#msg65213

And here:
http://ducatimonsterforum.org/index.php?topic=6218.msg106761#msg106761

And here:
http://www.fokust.com/gallery/fuel_pump

This is really simple/stupid but I have to mention it, because it's caused similar symptoms for me, twice.  (And, in my defense, my Duc tech once)

Thank doG the PO warned me about it, so that after 15-20 minutes of running my battery down and scratching a hole in my head, I remembered him mentioning it.
If I'm not really careful when I put the tank down, I'll get a crimp in the line that goes from the fuel filter down to that vaccum/petcock thing.  Sometimes, it's bad enough that once the float bowls run dry, it simply won't start.  But if it's just partially crimped, it will start and idle fine, but the second I get on it, it coughs and groans like Granda Simpson smoking a doob.  Lift the tank, the crimp is removed, runs fine, and will start again and run for a few minutes. Tank down, not so much.

Just a thought, check it out.  Believe me, I know how bad it sucks chasing your tail when the simple answer is staring you in the face and shouting "LOOK AT ME, DUMBSHIT."   

Quote from: dlearl476 on August 09, 2008, 11:09:24 AM
This is really simple/stupid but I have to mention it, because it's caused similar symptoms for me, twice.  (And, in my defense, my Duc tech once)

Thank doG the PO warned me about it, so that after 15-20 minutes of running my battery down and scratching a hole in my head, I remembered him mentioning it.
If I'm not really careful when I put the tank down, I'll get a crimp in the line that goes from the fuel filter down to that vaccum/petcock thing.  Sometimes, it's bad enough that once the float bowls run dry, it simply won't start.  But if it's just partially crimped, it will start and idle fine, but the second I get on it, it coughs and groans like Granda Simpson smoking a doob.  Lift the tank, the crimp is removed, runs fine, and will start again and run for a few minutes. Tank down, not so much.

Just a thought, check it out.  Believe me, I know how bad it sucks chasing your tail when the simple answer is staring you in the face and shouting "LOOK AT ME, DUMBSHIT."   

I like the theory, but would it have happened twice in a row with multiple reseatings?  I know that we were VERY VERY VERY careful when we were reseating the tank, but I'll certainly take a good look at this.  I do have a rather large battery crammed in there, but the lines coming from the fuel tank are at the back and the battery is at the front.  I will inspect the length of it, though, to ensure it is open the whole way.

Quote from: Ducatista on August 09, 2008, 06:36:46 PM
I like the theory, but would it have happened twice in a row with multiple reseatings? 

On my bike, it happens every time I lift the tank and put it back, unless I physically guide the hose away from the vaccum petcock thing.  Especially since I installed a new line when I did the FCRs.  At first, I had the fuel filter clamped too tight in the clamp and it' wouldn't turn.  AFAIK, it needs to, so that it can rotate and let the hose lay correctly, without a crimp.  Another thing to look at, if your filter IS clamped tight like mine was, that could be an issue as well, putting a crimp right there when you put the tank down.

Quote from: dlearl476 on August 10, 2008, 10:02:10 AM
On my bike, it happens every time I lift the tank and put it back, unless I physically guide the hose away from the vaccum petcock thing.  Especially since I installed a new line when I did the FCRs.  At first, I had the fuel filter clamped too tight in the clamp and it' wouldn't turn.  AFAIK, it needs to, so that it can rotate and let the hose lay correctly, without a crimp.  Another thing to look at, if your filter IS clamped tight like mine was, that could be an issue as well, putting a crimp right there when you put the tank down.

I'll take a peek.  Thanks for the hint!

So I ordered the parts for a fuel pump rebuild.  I'll let everyone know how it goes and hopefully I'll take enough good pics to post up in the how to section.