engine sputters and won't rev properly under load!

[zippinaround]

ok so heres my problem i have a 66cc HT with an nt carb, it idles fine and revs up perfectly with no load on it but once i leave out the clutch it just sputters and wont rev. if i try to rev it then lower the revs it fires fine for a bit then goes back sputtering i've already changed the plug, cleaned the carb, adjusted the needle , checked for air leaks, properly gapped the magneto all of which had no effect any suggestions?

 

[Pablo]

So:

a) are you really sure you are getting even fuel flow through your fuel valve all the way through the jet?
b) are you sure you don't have a leaking head gasket (low compression, it might run but like no torque)

 

[crassius]

clean it well & look for oil showing up near head gasket and along the case seams and at the crank seals

also, blow thru your muffler to check for no restrictions there

 

[Pablo]

clean it well & look for oil showing up near head gasket and along the case seams and at the crank seals

also, blow thru your muffler to check for no restrictions there

Great point on the restricted exhaust.

 

[zippinaround]

took off the carb again earlier and it was full of crap turns out theres a hole in my fuel filter will gat a new one tomorrow and see if it works. the air filter was also covered in oil so i cleaned it best i could. will post tommorrow after i fit the fuel filter. it might be the exhaust alright cuz its a homemade one and whoever made it tried to bend it without heat causing a very flat spot in the pipe!

 

[zippinaround]

got a new fuel filter it ran better for sure still not perfect but driveable i also mixed up some fresh fuel at 32:1 runs much better now ! just checked the plug there and its a very light tan and i was running on the 2nd notch from bottom tan is lean right?

 

[crassius]

tan is good - dead white is too lean