Fuel issue, topend studder, getting annoyed

ibcnya · #1 02-13-2009, 05:23 PM

This has been giving problems for days now. The bike will run great at 1/2-WOT throttle but under half throttle it studders. Then if i run it open to long it will studder more. Ive noticed that my fuel filter is filling up and not running down under load. I dont know I need help....new carb, or something. I feel like I work on this thing more than I ride it. Ive replaced everything from the jet in the carb to the whole engine assembly. im on my third tank of fuel and running the bike at 4oz/gallon 32:1 of 87 unleaded. The carb has Delortto #68 main jet in it and the needle clip is on the 3rd slot from the top. On the first and second slot the engine bogged off idle. On the third slot, no bogging. my plugged is gapped at .022 and im using the stock airbox. Can anyone tell me why the carb would spit fuel back outta the carb inlet? I had the filter off the other day and if givin constant throttle the carb would begin to spit fuel back out. This is fouling up the filter, and making a mess. I dont have a air leak and all my gaskets are good. Any help would be great. Thanx Billy.

TexasDav · #2 02-13-2009, 05:33 PM

wow how frustrating. I had a problem when I would go full open it would run fine then bog out and even die. I asked for help here on the forum and they said check my motor mounts and sure enough it was just slightly loose and the vibration was causing me all the problems. Now that might not be your problem, I am just throwing it out there. Good luck, I hate not being able to track a problem down.

Pablo · #3 02-13-2009, 06:48 PM

Shut the fuel off at the valve.

Disconnect hose at the carb inlet.

Hold the hose in a metal can or glass jar or fuel safe plastic. Turn valve on. Fuel should flow freely.

If no, get new valve. If yes, remove carb.

Take carb off, remove float base. Blow out and clean inlet actuator valve. Assure no gunge is caught.

Clean main jet (sucker should be clean)

Reassemble. Ride. Hard. Shut off. What does plug look like/

ibcnya · #4 02-13-2009, 11:37 PM

Ive had to do what you just suggested the last three times I ve rode it. Works fine for a few miles then studders up again. The plug is a pretty brown perfect burn color. I completely took the carb apart last yesterday, blew the main jet out, made sure the carb was cleaned, cleaned the tank petcock filter, drained the tank, recut another gallon of fuel, cleaned the air filter, tightened my engine mounts, changed the plug, regapped the plug, and still the same thing....pulling my hair out. I get a good few miles of riding and then ....duh, duh, duh......bawaaaah, duh, duh, duh. Sux....

Pablo · #5 02-13-2009, 11:46 PM

The fact that it's OK after you do that and then goes to ****, repeatably - says something.

Gotta still think of an air leak or some heat related problem.

ibcnya · #6 02-14-2009, 12:01 AM

Is it normal for the china carb to blow fuel back out the carb? Ive checked for air leaks....preignition maybe, can a 2 stroke have detonation?

POPS · #7 02-14-2009, 01:48 AM

Plugged exhaust ?... I had a car that would run fine for 30 min. than run like # than die. Would not start until cold than repeat the same same. Turned out to be the cat.converter. When it would get hot the stuff would expand in the cat and choke it to death. Do you have the cat.muffler? Could your muffler be plugged at the head ? Just a shot in the dark...POPS

glacknoid · #8 02-14-2009, 01:56 AM

I had a problem with fuel blowing out my carb and the problem was the tank wasn't ventilating. It would run fine for awhile till the gas in the tank would shake around long enough and build pressure forceing fuel into the carb overpowering the floats ability to stop flow causing it to quit and blow gas out the overflow. Check to see if your tank is venting.

glacknoid · #9 02-14-2009, 02:07 AM

Also a tank that doesnt' vent wont let fuel flow very fast before the pressure gets built up from aggitateing it but when the pressure builds look out it will flow till the pressure is released.

Walter F. · #10 02-14-2009, 09:42 AM

Quote:

Originally Posted by TexasDav

wow how frustrating. I had a problem when I would go full open it would run fine then bog out and even die. I asked for help here on the forum and they said check my motor mounts and sure enough it was just slightly loose and the vibration was causing me all the problems. Now that might not be your problem, I am just throwing it out there. Good luck, I hate not being able to track a problem down.

Dang TexasDav I was gonna say that. What does "sparky" the plug say???