lifan 125cc running realy shit...

[Ryzzy]

iv got a lifan 125cc and it will not rev over about 2000rpm.
the whole electrical system (stator, coil and cdi) r all sweet. I have tried 2 new mikuni carbies on it and there is no difference. it has the right amount of oil, the clearences r set properly the valves r seating right and the timming is correct, and it has new rings. and still it runs like shit....Anyone got any ideas?

 

[Custom]

ok..that dont leave much..is your exhaust blocked?

 

[cass38a]

My bet would be CDI. I know you have replaced it but I once put a new one on my bike and it was stuffed from new (pegleg did the same).

 

[darb110]

yeh start with electrics go over that again then move onto the engine...
what does the bike actiolly do when u rev it?

 

[Ryzzy]

i checked the electrical system. the resistance from the stator is fine, checked all the plugs and tried multiple cdi's and coils. so its not the electrical system.
it only revs to about 2000 rpm then shits its self and will not go any harder.
ill whack another top end on it and c how she bangs. if that doesnt work it looks like it will be a spare bottom end for my 140.

 

[Custom]

does it bang, shake, rattle or roll? any sort of mechenical noises?

 

[cass38a]

Is it running bad at a throttle position or is it RPM where it carks it. (ie will it rev out in 2nd at half throttle but run like crap at the same speed in top at full throttle)

 

[Chewy]

Have you checked for a sheared flywheel key?

 

[Ryzzy]

at about 2000 rpm regardless of throtle position it just doesnt rev out any harder, it sounds like it is spluttering and strugling to get induction. under load it is compleatly gutless and if its put under to much load it just dies untill u drop it back a gear. ill check the key on the shaft, although if that was brocken the timming would be off through the whole range but it still idles fine. so yeah im pretty much stumped.

 

[ducar.r.spec]

whats ur inlet manifold like?

 

[pb performance]

have you checked your fuel tap and fuel line ??

If you take your fuel line off the carby and turn the fuel tap on does the fuel
pour out with a stream the same size as the ID of the fuel line or does it
just trickle out ??

 

[Chewy]

There is meant to be a little plastic spacer that goes under the needle clip on the mikuni carbs, is that there and in the right spot?If it is not there the bike will run excessively lean.

 

[Matty]

its gonna sound stupid but check your spark plug...same happened to me a while ago and there was something stuck between the terminal things on the plug and it was interfering with the sparkk...