Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Low speed hissing and jumping

[ShakMan]

Hello all,

Another query ...

When I riding slowly, usually when coasting pass traffic at a contant throttle, I sometimes get a hiss, similar to a misfire, and the bike sort of jumps forward. Not sure if this is normal or is a result of the hot weather, but anyone else seen this or know of the problem?

Thanks.

[sevenfourate]

Boa constricter stuck in your inlet tract

??????????????????????????????????????

[ShakMan]

Seriously, it does sound like a snake !

Its obviously some sort of air being expelled, I'm just concerned its a broken engine gasket or something.

[andyb]

I would pay and get the fuel system set up at say jhp.
I had that today after my 998s was doing that. It now sounds like a completely different bike, so crisp.

[Harv748]

I've had a similar problem with mine since I bought it second hand. The problem only ever happens when on a neutral trottle at low revs (i.e. through traffic, built up areas etc.) Similar to the things you've experienced...more of a hiccup than a missfire, like a pop/hiss, and as you say the bike just slightly misses a beat and transmits a slight jolt forward. I'm also aware that I seem to be able to feel it through the trottle, as if when it happens the trottle just jolts in my hand a bit (am i going mad?)!?! And it only does it once...pop/hiss then fine.

When I took my bike to OYB for its 12k service, they tweaked the mixture (I think) and it made it worse...it was almost unridable at low speed through traffic, so when I took it back they changed things back...and it definately improved about 80%...but it still does it now and again, maybe once or twice a ride.

I've learnt to live with it...but I'm hoping that maybe this winter some clever chap will be able to solve it when its serviced (Nelly)?

Any ideas?

[Edited on 14-7-2003 by Harv748]

[Karl]

Harv
It just might need the TPS/mixture setup properly by someone with a little more time on their hands, last time I did mine it took me 3 hours to do.
If you want to I have a look at your TPS and mixture settings for you this weekend and we can go for a ride afterwards to tweek out the problem.

[matt748]

Shakman,
I had exactly the same problem on my 748.
Took it to Snells and they spent a couple of hours setting up the injection system. Sorted it out, and it hasn't 'hissed' at me in over a year now!

Matt

[skidlids]

Could also be down to excessive end float in the jackshaft that effects the timing, only applies to bikes with the 1.6M ECU

[ShakMan]

Thank god ... I'm not the only one.

Cheers everyone ... looks like I'm gonna have to book the bike in once more ...

[ziggi]

.... and it also happened after my first service. They adjusted the mixture and CO levels and then it was crap at low speed.

Took it to Sigma Performance and got FIM Ultimap. Runs rich now but never had a problem since and transformed the bike.