Fuel issue, topend studder, getting annoyed

ibcnya

New Member
Oct 29, 2008
220
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Concord NC
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

New Member
Aug 19, 2008
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Houston
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

Master Bike Builder & Forum Sponsor
Dec 28, 2007
3,664
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Duvall, WA PNW
www.sickbikeparts.com
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

New Member
Oct 29, 2008
220
0
0
Concord NC
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....
 

ibcnya

New Member
Oct 29, 2008
220
0
0
Concord NC
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

Member
Sep 8, 2008
311
0
16
Vancouver Island BC .Canada
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

New Member
Oct 22, 2008
184
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robbinsdale MN
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

New Member
Oct 22, 2008
184
0
0
robbinsdale MN
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.

New Member
Jun 4, 2008
326
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Connecticut
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???
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
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pampa texas
before you pop a hole in the cap look and see is thee any fuel leaking out of the cap area? All my tanks seem to leak a little fuel if filled up to high so if you have any fuel leaking out around the cap area poking a hole in the cap is not going to fix the problem.
I think you said you have a nonstock carb so I'm not going to be able to help I haven't messed with the after market carbs.
I reread some of the posts and I'm wondering is the float level set too low it runs fine for a little while then starts stumbling?! Or you might have a float needle sticking and starving it for fuel. There should also be a vent on the carb. On thechina carbs the opening for the vent is under the aircleaner right by the pivot arm for the choke I haven't run into one being plugged yet but it could cause a fuel issue if it happened to get plugged. If you still have the stock carb try it and see if the fuel problem goes away.
Norman
 

ibcnya

New Member
Oct 29, 2008
220
0
0
Concord NC
before you pop a hole in the cap look and see is thee any fuel leaking out of the cap area? All my tanks seem to leak a little fuel if filled up to high so if you have any fuel leaking out around the cap area poking a hole in the cap is not going to fix the problem.
I think you said you have a nonstock carb so I'm not going to be able to help I haven't messed with the after market carbs.
I reread some of the posts and I'm wondering is the float level set too low it runs fine for a little while then starts stumbling?! Or you might have a float needle sticking and starving it for fuel. There should also be a vent on the carb. On thechina carbs the opening for the vent is under the aircleaner right by the pivot arm for the choke I haven't run into one being plugged yet but it could cause a fuel issue if it happened to get plugged. If you still have the stock carb try it and see if the fuel problem goes away.
Norman
Yes I do get the fuel leak at the cap, it is a stock carb and the vent for the carb sometimes will spit fuel out there.... I to thought about the float bowl level, byut wasnt sure on adjusting it so I didnt mees with the arms yet. In case you missed it I swapped the stock jet out for a Delortto #68.
 

glacknoid

New Member
Oct 22, 2008
184
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robbinsdale MN
you shouldn't have to poke a hole in the gas cap they are already designed to breath with vent holes on the underside that lead to the outer ridge of the cap when installed so if you do fill it up too much some could come out the vent holes. I don't think your cap is the problem if it's venting properly.
 

ibcnya

New Member
Oct 29, 2008
220
0
0
Concord NC
Went and played some more. I rode it for a mile then it started again. I noticed the fuel level in the filter doesnt change if I hold the throttle open. When I first got the bike finished the carb wouldnt waste any time sucking that fuel down. I dont think its the #68 jet either because it was doing it before I swapped jets. The reason I swapped jets is because I broke the stock one cleaning the carb trying to resolve this problem.
 

alkllimike

New Member
Nov 13, 2008
19
0
1
Pima Az
get rid of the fuel filter. I have a model t and put a filter on the tank but there is not enough pressure in a gravity fed system to push the fuel though the filter, When I took the filter out it ran fine. mike