Ducati Monster Forum

Ok here is the story:

2 weeks ago I dropped my bike at stop light.  Bent the handlebar, no other damage.  Took the handle bar off only to discover a frayed throttle cable.  Ended up pulling off the gas tank, airbox, and carbs to put the new cable on.

1 week ago get the bike running and all is well except I am not noticing some slight popping when under 4K and trying maintain a steady speed.  Never remember it doing that before.  Only thing I considered was maybe an exhaust leak.

Today I decide to spray the exhaust with water and soap while it is running to look for leaks.  Bike  is hot while I am doing it, but nothing happens and don't seem to see any leaks.

Bike is idling around 1400 RPM so I decide to lower the idle screw a little.  Go too far and bike stalls.  Attempt to put screw back to original position.  Start up bike and now it idles fine, but stalls when I blip the throttle.  What the hell?  Bike continues to stall no matter what adjustments I make to the throttle screw.

Now the bike won't start at all.  Only turns over and over and over.  Beast with two backs.  Any advice?  I am totally baffled.

Joshua

drain the float bowls to check for stuff other than fuel.

make sure it hasn't got some sort of fuel blockage.  crimped hose from the tank being up, failed vac tap, etc.

Thanks for the quick reply.  Will the drain the bowls to see what comes out.  What is a vac tap?

Also to clarify I rode the bike for 3 days after putting it back together.  It had no stalling/starting issues until I played with the throttle screw.

Ok I drained the float bowls.  Fuel was clear however it seemed like only a little came out.  Seem to remember a lot more fuel in the past.

I actually measured the gas.  Both bowls only had 1 tablespoon (15ml) combined.  Is that right or should there be more?

There should definitely be more than 1 tablespoon for the two combined. Based on my super-scientific estimation techniques (trying to think of how many shot glasses worth of gas would fit in the float bowls), I would guess maybe 4-5 fl. oz for both (120-150ml).

It sounds like you are not maintaining the correct fuel level in the float bowls. The question is why. Likely suspects are usually a weaker than normal fuel pump, a failed or failing vacuum petcock, or a kinked line when the tank is closed. You can check the petcock by bypassing it, but I'm not entirely sure how to definitively check the fuel pump. My guess is that your fuel pump is probably not working like new, but also probably not the root cause of your problem. Fuel pump rebuild kits can be had for <$20, and would probably not be a bad idea for preventative maintenance at least (see http://amzn.com/B000ONZTM2 (http://amzn.com/B000ONZTM2) for where I bought mine).

The petcock or pump would address your idle issues. However, your original problem of fuel starvation when maintaining a steady speed can be caused by the carb vent hose(s) that goes to the side pod(s) being disconnected (not quite sure what to call that hose, also not sure if there is more than one typically. The PO of my bike made a few changes, and there is only one on my bike, but YMMV). This has happened to me before. When the end of that hose is left exposed to the moving air, the pressure in the hose becomes too low, and results in insufficient fuel delivery, popping, and generally running like shit when maintaining a steady speed. So check and make sure that the side pods are connected.

Here's a quick tip that I think may come in handy for you: you can fill up the float bowls using the fuel pump without the engine running as long as you have bypassed or replaced your vacuum petcock and have a $4 siphon pump available. http://www.ducatimonsterforum.org/index.php?topic=53585.msg991070#msg991070 (http://www.ducatimonsterforum.org/index.php?topic=53585.msg991070#msg991070) . I typically do this whenever I drain the carb float bowls. After doing this, you don't need starting fluid or gas down the carbs to get it to start; you just start it like any other time.  Also, once you have fixed your fuel issues, you may want to sync the carbs now that you've adjusted the idle set screw.

Good luck with everything!

Since this problem started after a drop I will try to narrow in a bit on bond0087's excellent post.

First I would change the fuel filter since it is a maintenance item anyway, make sure the vacuum lines going to the pump and fuel shut off are good and check that my fuel and vent lines from the tank are not kinked.  The vent lines from the carbs may cause problems at speed, but so will a shortage of fuel to the carbs so work on that first.  Also, see if the symptoms change with the fuel filler cap open (not while riding).

Thanks for the wonderful posts everyone.  After much reading on this forum I figured it was either a stuck float, bad pump, kinked lines or bad petcock.

Like I said above all that I did was drain the floats and let the bike sit for awhile to cool off (starter was getting pretty hot).  I also double checked all the fuel lines and vacuum lines under the tank to look for kinks.  Waited a few hours and decided to turn the bike over to get the bowls filled up with fuel.  After a few minutes it started right up!  My idle was pretty high from all the adjusting I did, so I set it back to 1200 RPM.  Bike seems to rev fine now and doesn't stall.  The only thing I can think of was maybe I had a kinked line, or maybe I had a stuck float and draining the bowl helped un-stick it.  Strange.

I decided to toss in some new spark plugs this morning (after the motor was cold again).  The upper spark looked good, but the lower spark was oily and black.  Could the lower spark got fowled up from me dropping the bike on its side?  Anyway going to take it for a spin this morning and see if new sparks help with the popping at low RPM.

Update:  the new spark plugs made a huge difference with the popping/surging when maintaining speed less than 4K RPM.  Really happy.