Weber DCNF Problem

Hi, I'm new to this forum and to be honest don't have a Ferrari but I do have a Ducati 900SS with a Weber 44DCNF carb fitted which I believe is also fitted to the 308?

Anyway I'm having big problems with this carb and can't find any answers on Ducati Forums so thought I would try here.

For about the last 18 months the carb has been flooding the crank cases with fuel when the bike is turned off. I've fitted a full new service and gasket kit from Eurocarb and also set all the idle and balance screws to factory settings and this still hasn't helped. With the top off the carb and the float bowl full of fuel the level of the float bowl can be seen to drop by a couple off mm per day until only 3-4mm of fuel is left in the bottom, the fuel appears to be running quiet freely through the idle / low speed circuit and down over the butterflys.

Has anybody had this problem? and if so how did you get rid of it. The bike is normally run on 95 octane unleaded fuel.

Thanks in adavance

Andy

 

Hi Jim, Thanks for the reply

As far as I can see the float height is to the factory figure but I have had an issue with the fuel supply to the carb not shutting off ( the return line had a leak internal to the tank and was giving a constant supply). I normally prop the bike up straighter than it would be on the prop stand alone.

I think I do need to put the carb on the bench and get a supply going to it but might put some food colour in the fuel to help see where it is coming out.

Thanks for your input

Andy

 

dwil: I'll defo look for a fault in the casting but I'm gonna have to be careful in the future till I get this fixed not to hydro lock it

JohnMH: My duke is a 89 version so has belt drive and basically the same as the one your talking about apart from the carbs which are Mikuni on the later bike. Unfortunately I can't retro fit Mikuni's, which I would love to do, because the battery position also changed preventing this.

CliffBeer: It's more than evaporation as I've just let about 100ml of petrol out of the sump (I don't leave oil in the bike at the moment). The idle circuit from what I can see seems to rely on fuel surface tension to stop it leaking out and I was wondering if the new 10% ethanol fuel had a lower surface tension (this problem started about 18 months ago which I think is about when this was introduced?) and this was now causing a common problem. At the moment the bike is level on it's paddock stand.

Looks like my best route now is to get the carb off the bike again and hook it up on the bench and make 100% sure where the fuel is coming from (incase of a casting fault). I think my main question has been answered on here that this isn't a common fault and I need to do some further investigation my self on the bench.

Thanks for your replys guys it's great to find a friendly forum.

 

Yeh carb has had a complete recon kit including float valve. Didn't run any fuel through the carb when it was off last time but I think that's got to be the next step.

 

Thanks Jonathan they are more detailed than the drawings I currently have and should be a great help. I'll let you know how I get on this week.