Hi all!! Having a few problems with my 04 250 sherco. The last trial i did my bike decided to start hunting for fuel or air (not sure which) which gave erratic idle. It then cuts out. I assumed it was a blocked fuel filter or some crap stuck in the carb so I stripped it and cleaned it out. I put it back together to find this did not work. The air filter and box is clean so now I'm stuck for ideas. Any help will be much appreciated.

Thanks!

Sounds like pilot jet is dirty or water in carb. Really need a compressor to blow out dirty carb drillings and jets.

Remove and clean the pilot jet. You willl need to blow compressed air through the pilot carb drillings as well. Make a note of how many turns the air screw is positioned from fully in, then fully remove the screw and also clean out the airway with compressed air. Reassemble back to position already noted.

While the carb is stripped clean out all jets and passageways with compreesed air.

Thanks for reply. I cleaned the carb with compressed air took everything apart and cleaned inside. the only thing I didn't take out were the idle screw and the mixture screw maybe I should do this.

Thanks for reply. I cleaned the carb with compressed air took everything apart and cleaned inside. the only thing I didn't take out were the idle screw and the mixture screw maybe I should do this.

It is recommended, as well as well as actually passing a fine wire through the jets to clear them. the pilot jet can be difficult to see through and also decieve you with a bit of crystal sand! The tiny passages in the bore if the carb as well.

Water in your fuel supply can re- contaminate things as well, ck your jug and pour your last bit into a clean vessel just to test!

Lessons learnt! Mostly the hard way! Might be surprized what you find at times!

Copemech.

Got to agree with the water in the petrol tank.

I used to think that the water was getting in to the carb through the airbox but I'm convinced more than ever that it gets in through the petrol tank now.

Water in the airbox has always been muddy and dirty but when I've had water in the carb it has always been clear like tap water.

Not sure if it's coming from the fuel companies or from me washing the bike with a pressure washer.

I guess I'll have to strip the carb again as well as using the fine wire. As to the water in the fuel is this easy to spot?

Absolutely really easy to spot as the water does not mix with petrol and forms in to droplets in the bottom of the carb float bowl.

Thanks John! I'll do what you suggested and check for droplets. If there isnt any and it still runs iffy with cleaning jets with wire would you hae anymore ideas. I've noticed you are part of richmond club do you get over do do many trials for richmond?

Thanks John! I'll do what you suggested and check for droplets. If there isnt any and it still runs iffy with cleaning jets with wire would you hae anymore ideas. I've noticed you are part of richmond club do you get over do do many trials for richmond?

One of the potential problems that you must get your head around is water condensation in your fuel supply, and your tank getting to your carby!

It will lie in the bottoms of all these vessels if it is pure gasoline, as we have alcohol induced fuel here, it is more dispursed and even more difficult to pin down at times. But, one would be well advised to empty everything into a clean clear vessle, I use a clear 2L pop bottle with the top cut off, cleaned and dried, break the carb bowl over it, then pour any remains. Closely ck what you got in the bottom.

Same with the tank, drain the good off the top on regular position, then switch to reserve and collect it, then invert to collect the rest!

The banjo screen on the dellorto should be ck'ed and cleaned, it is good on small particles(not water), yet does not prevent dirt entry from other points like the vent tubes or elbows. Long tubes on these are not recommended. Nix them, short tubes of a couple inches at max! Any blockage of air flow in the bowl vents or the tank vent itself is critical!

Your fuel can is next, sort it in the clear bowl!

All this is fundamental basics, but untill one is sure beyond compremise it can screw you up dearly!

Also being basic, most problems are resolved at that level, others being more advanced.

Edited September 13, 200916 yr by copemech

Ah a bit more of a detailed explanation cheers copemech you seem to know your stuff. When I've done what you suggested I'll post back. You mentioned shortenening the vent tubes, does this include the tube going from one side of the carb to the other (the one with the slit in the bottom) would this be a breather pipe or is it a vent pipe?

Ah a bit more of a detailed explanation cheers copemech you seem to know your stuff. When I've done what you suggested I'll post back. You mentioned shortenening the vent tubes, does this include the tube going from one side of the carb to the other (the one with the slit in the bottom) would this be a breather pipe or is it a vent pipe?

Those would be the fuel bowl vents. For some reason, tying them together at the bottom with a common slit in the hose sort of defeats the purpose of having two of them in the first place.

Many run no hoses at all on these. I run two hoses about 50-60mm long mainly to deflect dirt or water a bit better. Opinions will vary, but restrictions in these or trapped fuel can cause problems.