Nervous Engine below 2500 rmp

[Menno]

Hi there,
Riding a 906 for a couple of weeks now and I do have a (minor?) problem with it.
When riding under the 2500 rmp and when I want to accelerate the engine holds in and starts to backfire a little bit. When opening throttle very, very slowly, there's no problem.
It's also a bit non responsive on the throttle after closing it and opening again at higher speeds.
When opening more than 1/2 there's now problem at all. Goes like a lunatic!
Does it sounds familiar to someone? Is it the Weber or should I search somewhere in the electrics?
Best,
Menno

[persempre907]

Welcome Menno,
I'd say that less than 2500 rpm are very low for a carbed V twin, so that you can't pretend a smooth acceleration.
On my 906 (less on the 907), the bike used to jerk along.
No matter, it's really hard the tuning of the Weber...
Ciao

[jcslocum]

Menno,

Sounds like the carberettor needs to be tuned and the throttles balanced. Riding the engine at this low RPM will also make the engine very "jerky" and it will shake a lot. Keep the revs above 3500 RPM all the time and it will be smoother.

[Mc tool]

I agree with the above comments in that they are a bit poxy at low ish revs , but if you are into "fiddling" I would check the fuel flow from tank to carb ( as a matter of course ) but mostly I'd be interested to confirm that both accelerator pump nozzles are discharging. remove air box , look down throttle bores and open throttle and you should see two squirts of fuel ( one per venturi ). you dont say how old the spark plugs are , or how long since the valves were "done "
Ps the accelerator pump test should be done with the motor NOT running. Ha ha ha I just had this mental image of some guy with an eyeball hovering over each venturi ( there about the right distance apart ) tweakin the throttle coz if it decides to spit back , which it will probably do without the air box assy............. the injury ( whilst hysterically funny to any bystanders ), would not be nice , and it is difficult to explain to everyone where all your face hair went
Good luck

[ducapaso]

Have a look to my suggestions for carb tuning in the 750 F.A.Q. post

[JWilliam]

Hi there,
Riding a 906 for a couple of weeks now and I do have a (minor?) problem with it.
When riding under the 2500 rmp and when I want to accelerate the engine holds in and starts to backfire a little bit. When opening throttle very, very slowly, there's no problem.
It's also a bit non responsive on the throttle after closing it and opening again at higher speeds.

These Ducati twins don't feel great below 2500 rpm at the best of times. When you mention the throttle lag at high rpm, I get that too, don't know why - its the sort of throttle response I would expect from a 2 stroke. The Weber can be tweaked somewhat, the other things to check are the standard ignition coils. If they have too low an impedance on the primary coil they will overload the ignition unit causing backfires and poor timing throughout the rev range.

[Menno]

Hi Guys,
Thanks for the comments so far. Think I will start with the Weber. Allthought it might take a little while because last weekend the cluch broke down. The pressure cilinder (slave) has found a way right through the pressure plate! Completely worn. Ordered some parts; new cilinder and a used pressure plate. Have to fix that first. We have to keep on riding of course.. Keep you posted.
Menno

[ducbertus]

Hi Menno,

Maybe you check your fuelpressure too.
I had a 900SS with weber. No fun.
it profed difficult to the card.
later I read somewhere that Ducati had "forgotten" to build in a fuel pressure regulator, which probably could have cured my problems at that time.

good luck

Ducbertus

[jomo]

Start with new spark plugs and work from there. Cheap things first!