I took my paso906 on Friday out to do a big maintenance (change belts, cooling fluid, all other oil fluids, and filters, check torque on cylinder nuts ect.). Bought the 906 2 years ago, made 1000km (now 29’000). I decided to do so because I have no service history. When I tried do Star it (to warm up for changing oil) it became to much Gasoline. Later on I could start it without problems.
Doing maintenance I realized 3 things

• Doing maintenance on a 906 is much more time consuming than on a 750
• There was quite a lot oil coming off (more than 3.5 l, which had a strong gasoline smell)
• I found a kind of selfmade reduction on the waste fuel rubber pipe wich is connected to the underside of the fuel tank.

First of all has anybody an idea how the Gasoline has come into the oil? I did checked the floater. It seems that it closes just when the floater is on the most up possible position. How can I check easily weather the valve really closes? , resp. is there an easy way to find the correct position? ( On the other hand I don’t want to change much because the 906 runs marvellous)



Concerning the selfmade reduction on the waste fuel rubber pipe, has anybody a clue what this is for ? (perhaps to increase fuel pressure??)


Any good hints are welcome,
regards pasoalf

Hi Pasoalf,

Fuel in the oil is usually because the carb is flooding or over filling to use another term, the float action on/off may seem ok, but the float needle could be sticking open under fuel pump pressure, 1st thing is to clean everything reassemble and try again, I once drained 5 litres out off my 750 sport engine through the float needles sticking on, and fuel pumping past the inlet valves and into the crankcase's, it certainly gave it a good clean out I knew straight away what the problem was and simply replaced the float needles and problem was fixed, but this was on Keihin FCR's, the webber may be more complicated.

good luck with it

Cheers

Peter

Float level is too high. Bend up the tab until the float is parallel to the above carb plate. The jet within the fuel line is to maintain fuel pressure. You might as well leave it in.

Personally I'd take Higgy's advice and replace the needle and seat just as a matter of precaution as they are most likely the originals and would be due anyway, (sorry forgot to write the needle & seat, thanks Higgy ).

Also wouldn't hurt to remove the screw in plug (17) on the front cylinders header pipe as well, when this happens they can fill with fuel as well I again know this from personal experience.

Currently playing with a 1988 BMW R100RS that had been in storage for 5 years, and finding all sorts of interesting things to do to the carbs on that.

Cheers

Peter

you don't need the jet in the return line at all and most likely it is the source of your bad needle and seat. The standard pump has too much pressure and restricting the return line will only make it worse.The proper placement of a restriction jet is in the vacuum line that goes to the control unit on the 906( well sort of anyway).You may even find taking the restriction out of the return line might solve your needle and seat leaking issues if it is not too late.

I thought the restrictor went in the fuel feed after the "y" splitter to actually reduce the flow to the carb.

As Higgy sez ( sort of ) better off without it . I have the Y as close to the carb as reasonably possible and have the return line ( 1/4" ) dawdling from the carb to the tank . The resistance of the return line alone is enough to see a reasonably pressure at the carb . Some people fitted a restrictor ( jet ) in the return line , probly trying to increase fuel pressure to sort the carb issues , human nature ..... if a little fuel pressure is good then more has got to be better

Thanks for the inputs. For the time being I'll leave the reduction within the pipe, and I'll control the oil level frequently....
I'm a bit afraid change anything, because the 906 is actually running perfect.!!!
But I'm going to order a fuel pressure gauge. I've seen one for 33 euro with all fittings on.
Has anybody an idea what the fuel pressure of a 906 should be?

3-4 psi .
for some reason the float valve is not controlling the float level . More than likely this will not be evident when the bike is running ( you say it runs well ) . What is most likely happening is that when the bike is not running , and has FULL fuel tank , gravity is causing fuel to flow thru this leaking float valve , over fill the carb float bowl and then run into the inlet manifold , down thru the inlet valve , past the rings and into the sump . Its all very well to monitor the oil level but any fuel that gets into the oil will dilute it . If you remove some oil to get the correct oil level , when the engine heats up the fuel will evaporate leaving you with a low oil level , and fuel diluted oil will not lube the engine properly. I have seen a similar case where when the fuel started to evaporate out of the engine oil, the fuel vapour went thru the crankcase breather and into the air box and the resulting mix that made it to the engine was so rich it would hardly run until the excess fuel had boiled off . The bike would start and run ok till it started to warm up , then it got worse and worse ... hardly rideable .... then it slowly came right , until the next time the owner parked it up for a week.
Put a new float valve in it

I now took of the restriction inside the return line, and replaced the Oil. No difference, the bike still runs well. But when i Take of the Oil filling Screw, ther is still a strong gasoline smell (don't know if this is from before...) I also saw on the oil inspection cap, some white creamy fluid above the oil (just a little bit) I Really don't know if this is because of gasoline within the oil...? The Oil Level is still O.K. (did not increase) anyway, I'm just going zo order a new needle valve, and i closed the fuel cock, just to avoid....
Concerning needle valve, i did not find any under the Ducati No (037027010). But i found a Weber specialist in Germay, which is well sorted with parts. But it seems that there exist different diameters. Has any of you an Idea which is the correct one???

Diameter 1,25mm Bestell.Nr. 8800 Weber OriginalpartNo: 79405125-79501125
Durchmesser 1,50mm Bestell.Nr. 8803 Weber Originalnummer: 79501150-79405150
Durchmesser 1,75mm Bestell.Nr. 8805 Weber Originalnummer: 79501175-79405175
Durchmesser 2,00mm Bestell.Nr. 8807 Weber Originalnummer: 79503200
Durchmesser 2,25mm Bestell.Nr. 8809 Weber Originalnummer: 79503225
Durchmesser 2,50mm Bestell.Nr. 8808 Weber Originalnummer: 79503250
Durchmesser 3,00mm Bestell.Nr. 8819 Weber Originalnummer: 79503300

The white creamy stuff is because the oil is not getting hot enough to boil out moisture , short runs , cold weather , I wouldn't loose sleep over it

replace the needle and seat with the 79503.xxx where xxx is the size marked on the current jet size, the one you have should have its size marked on it. Can't read it any more go with a 79503.300

Simple test Alf. Take your air cleaner off and look inside the carby with the engine off but the fuel pump running (ignition on).If the carby is flooding,you will see fuel dripping from the centre of either venturi.
You may need a torch to see clearly.This is the first place it starts dripping from if the float is set too high or your needle and seat are faulty.It may even do this without the fuel pump running or only when parked on side stand.

It makes sense to me that the float may be set a little high as my 750 runs best,when the float is on the high side,but it too risky running much above the recommended setting because of fire danger. J.