Ducati Monster Forum

So i went for a ride with mates (on a private track Of course) and for a while all was good in the sweepers between 120-150. But then the bike lost engine power/spluttered a bit, and I had to coast to a stop. Numerous times it happened, when i slowed down enough below 100 or so, sometimes it regained power. Seems like an air/fuel/carbie issue? Had electrical power at all times. Bike is a 98 m750. Possibly related, I found the hose from the left carbie to the RH side pod had virtually snapped off below the inline filter. Could this be affecting one carbie? A couple of times it felt rather jolty, like running on one cylinder until it recovered and I could roll on.

Any ideas/suggestions?

You need to reconnect that hose. The pod gives still air for the slides to work smoothly. The slides may be erratic in operation.
The other pod may only be there for looks. My 900 had one hose feeding both slides going to the left pod only. The right side pod was for symmetry.

Fuel delivery may be an issue for sure if that dont fix it.

Definitely check your fuel lines from tank. They can be either pinched by tank or old and kinked not holding shape reducing fuel flow. I had issue and 100kph was the max speed capable with reduced fuel. Simple check and cheap to fix.

both of the above posts are what I was going to suggest too. definitely replace the fuel filter and possibly get new fuel lines if any appear kinked over or collapsed.
also would be a good idea to replace the inline fuel screen that is inside the inlet to the carbs (if your bike even has this installed still). link to the part I'm referring to: (page 18, part number 9)
http://issuu.com/ducatiomaha/docs/m750_usa-00?viewMode=magazine&mode=embed (http://issuu.com/ducatiomaha/docs/m750_usa-00?viewMode=magazine&mode=embed)

and yes, the slides in the carbs have vents which need to have equal and ambient pressure on one side of their diaphragm at all times. those hoses are these vent lines, and they both are supposed to lead to the right side gray plastic pod. if the vent hoses see unequal, or positive or negative pressures, the slides will not operate properly, and will usually operate unequally, making the bike run rough and low on power. if they see decent amounts of negative pressure, it will cause the slide to slam shut and stay shut as long as it has pressure. and whether the pressure is positive or negative, or fluctating it will often make the slides flutter making the bike incredibly jerky. cracked or heavily damaged vent hoses, or vent hoses missing altogether, will definitely cause these conditions. the filters are important too, they need to stay installed to prevent dust, bugs, and other debris from getting up into the air chamber above the slides and diaphragm.
I recently replaced the hoses on mine with standard crankcase vent hose from autozone. the ducati hoses are no longer available to buy, so you have to make your own. the hoses I bought were I believe 1 7/32" (31mm) inside diameter, to fit the nipples on the filters. the outside diameter was much larger than the original hoses though, so I had to drill out the holes in the gray pod. once I replaced mine I noticed a HUGE difference in power and smoothness on the highway, cruising and accelerating

Cheers guys. I don't think its a fuel line issue, I always check that for kinks when lowering the hose. Replaced the fuel filter recently. The 'still air' makes alot of sense, above a certain speed the air rushing past the exposed hose creates a pressure, affecting the carbs.

I think I best replace most of the rubber lines, they're almost 15 years old.

exactly, sometimes negative sometimes positive depending on the angle of the air travelling over the hole in the hose or the filter, and often pulsing, and almost always uneven between both vents (uneven slide operation)

So I'm gonna need some FCR39's to fix this yeah? [bacon]