Engine stutters/runs erratic

[mannyvillegas]

When I press on the accelerator real easy, the engine runs perfect. But if I press the gas pedal all the way down, the engine runs erratically. Is this a case of "too rich" air/fuel mixture, an electrical problem, carb (float) issue, air leak in carb or air leak in air filter box? It really got me baffled.

[mannyvillegas]

Oh, it's a G2.

[sho305]

Often a leak in the airbox will do that, not always. Any change to factory exhaust or intake will cause a jetting issue on most yamaha and you have to rejet. Could be dirt in carb too maybe ignition issue or fouled plug.

[mannyvillegas]

I played around with the air/fuel mixture. It didn't work. I'll try a new plug on the week-end.

[mannyvillegas]

New plug did not cure problem. Any ideas?

[groundpounder]

have you tried it with air box off see how it runs? also try a Little chock then tell us what it does? if it runs better one of those ways let me know

[mannyvillegas]

Removed air filter connection. Put on little choke. Even sprayed a little carb cleaner while engine is running. Same results. Runs erratically. Have adjusted valve clearance to .004. Have done everything that I could think of, have read here and elsewhere.

A mechanic friend advised me to check cylinder head tightness. Will do that today.

If still it wont work, I may have replace the carb as a last resort.

[GMB74]

Do you have a spark tester like this:

http://www.harborfreight.com/90-inli...cker-4445.html

to test the ignition system? If you can get it to act up when the rear wheels are blocked up off the ground, this is a safe and easy way to eliminate an ignition problem. A lot cheaper than buying a carb if it is not a fuel problem.

Have you taken the carb apart and tried cleaning it ? Was there a lot of corrosion or carb snot inside? Ethanol fuel has been doing a number on carbs these days.

[fishman296]

My '95 carryall Club car is also running erratic. Guy I bought it from had just replaced the carb (I even have the old one). The problem started when I switched to non-ethanol gas. This shouldn't have any effect on the problem would it?

Thanks for any help.

[sho305]

If it stays constant with fuel changes then I'd look at ignition weakness (happens at more throttle when there is more mixture to ignite) or a mechanical issue such as valve timing/leaking/lash (more obvious with less vacuum at more throttle) or maybe head gasket/compression.