fuel problem

[CPT Jack]

Last two rides I've had this problem. When I've got long fast stretch back to the truck, holding the throttle wide open, the engine will begin to gasp (for fuel I'm guessing), it "gasps" worse and worse until "bwwaaaaauuuuhhhhhh" (slowing, descending tone) ... *cough cough*. Engine doesn't die though - as soon as the rpm gets back down to 2-3000 rpm it continues to sputter along intermittently. This will be after running great for a 12-15 mile loop and again only on a fast stretch holding 3/4 - steady throttle.

Also worth noting is that after this occurs, even after a 20-30 min. rest, I can't start the bike for the life of me. :ugg: Req'd bump start last time.

I had a guy help adjust the float bowl for me so that's my main suspect. As it sits it will not dribble premix unless lying flat over. Doesn't spill a drop at a 45 degrees. Does this sound wrong?

Any other ideas? Sparkplug?, electrical?

Can't be jetting - we'll put in 10 -15 miles without a prob., bike running great, before it goes into fits.

thx for your help.

 

[David Trustrum]

Can't be jetting

I don't think it is but Never say can't.
Well only if you are holding it wide full open for the same amount of time in the first few minutes, but unlikely would start to nip up several times without going whole hog.

Fuel supply is the likely culprit. Try opening the float bowl screw & see if petrol will flow continuously. Who cares if you waste a litre? This will rule out blocked petrol cap, carb vents & the fuel hose crimped by that fuel filter you put in that collapses the hose when you put the tank down. We’ve all been caught by that one.

You can always adjust the float until it does dribble a smidge & back it up.

Not restarting is confusing though. Check just after it happens turn off the fuel as you coast to a stop & open the float bowl. If it is full then you may have a coil (ignition or stator) that is breaking down under heat.

 

[bigred455]

Good suggestions by David.I would also take the carb completely off the bike,take all the jets out.Spray 2+2 or any carb cleaner through all the jet passages and the jets .Spray inside the fuel line that leads to bowl as well.Clean the float needle and pin also and double check the float height.Start tilting the carb until the needle seats all the way, not totally upside down this will cause the pin to drop the floats even more and give a false reading make sure the little pin is still extended resting on the tang of the float.Your manual should give the the float height,but majority of the time it should be parallel with the carb mating service.Throw the carb back on the bike and see how she runs.Still boggs on you change out your fuel,still boggs on you, check electrical.Make sure the kill switch is also clean .1 THING AT A TIME THEN TEST.By the way what kind of bike is it.

 

[viking20]

Also,when dealing with these kind of problems:remember your fuel system starts with the air hose in your tank lock and ends with the reeds!A small piece of dirt blocking the end of one of the tubes(incl the ones on the carb),can have a major effect.A friend of mine once struggled for weeks with his sons new bike,and ended up getting a new bike once again,turned out the tube from the tank lock was blocked,so gas couldnt run properly to the carb!

 

[CPT Jack]

Hey what happened to the sig lines? My bike is a 2001 GasGas XC250. I had the carb fully apart 2 weeks ago for a thorough cleaning. Reeds were perfect. Also replaced the fuel hose. I'll check that gas cap vent first off. I never considered that.

thx

 

[bclapham]

jack, check your carb breather hoses also..they can quite esilly get blocked.

what about airleaks? crank seals, airboot-carb manifold?

 

[Brian]

I had similar problems the last two times out. It was extremely muddy, and after running hard, the bike would start idling fast, and act as if it were running out of fuel. It turned out that 2 of the 3 carb breather hoses were clogged with mud. I haven't been riding yet after I cleaned them out, but I suspect that was my problem.