[TijmenK]

Good evening Ducati.ms members!

I am currently working on my project bike; a Ducati Monster 1996 from 1996. After having replaced multiple items and have the engine running again I ran into a all kinds of new problems- one of which is a sudden spike in RPM when on light throttle.

When I start the motorcycle and let it idle (no choke, very light throttle ~2000rpm) the engine increases RPM drastically on its own. This is without moving the throttle at all. When riding the bike in 1st gear slowly through the streets with the clutch engaged the same problem arrises; the bike suddenly increases RPM a lot without throttle input from me.

I am currently at a loss what the problem could be, hence why I posted to this forum. I hope you're able to help me!

 

[belter]

is it the step in ignition advance?

 

[duc96cr]

Are you sure it’s running on both cylinders ? That sounds as if one cylinder may not always be firing. Does the engine sound change ? Does power increase dramatically when this happens ? If the engine is cold when this happens that’s a possibility. Run some SeaFoam through it and readjust your mixture screws when well warmed up. You may end up at 3 or 4 turns ccw and that’s ok. If the revs hang when warm open the mixture screws another 1/2 turn ccw.
Also make sure your plug wires are seated firmly in the coils and caps and your plug caps haven’t unscrewed.

 

[wiklund]

The stock old school ducati ignition makes a drastic advance in ignition around that rpm which makes the rpm rise when free-revving/applying ligh throttle while in neutral without actually changing throttle input. This is also what at some times makes these old bikes idle hang i stop lights etc as well.

If you ride in for example 2nd gear with slight throttle applied and listen carefully you'll hear engine tone change as the ignition advances.

Worth mentioning is that the carby bikes never really liked puttering around near idle in low gears.