bike not reving properly

[marty7n]

Hi all new to this site.recently a good freind dropped his bike over to me to try sort it out, it s not the healthiest but id rather try get it runin for him than turn him away to be robbed.

The bike is a jap small wheeled pit bike, all black fairing, engine is a lincon 4 stroke, not sure what size as no stickers or paperwork came with it, it has a mikuni carb with enricher/choke it only starts with the choke fully on, when choke is switched off after full heat up it cuts out, the main jet screw is out around 7full rotations I tried adjusting it in and out in every way possible, all I get is a back fire when to rich and hits a dead point halfway up through the revs like its on a limiter, even with choke off it does this? Any ideas lads? Cheers.

 

[timeeh]

Air leak? Get idling again and spray round the inlet manifold, if the revs change then u got a leak (wd40 works for a spray). Also try cleaning the jets in the carb with carb cleaner and a air compressor.

 

[DHZ_XR8cing]

As Timeeh said clean the carb out. If fuel sits in the bowl long enough it evaporates and leaves a residue that will block the jets. Soak it in some carbie cleaner if its real bad inside.
Sounds to me like a blocked main jet. Take the bowl off and unscrew the jets and see if you can see through them.
The mixture screw should not need to be wound out anything past 2.5 turns. 1 1/2 turns makes a good starting point.
Drain the tank out and flush it out with fresh fuel and refill.
Keep us posted

 

[marty7n]

Head is tight, no leaks engine fires fine just not geting full rev band with choke off.

 

[marty7n]

Carb was cleaned by the old man, will blow it out with the compressor 2m, any idea what year lincoln engine it is? Itsa vertical 4 stroke I noticed the new pit bikes are horizontal.

 

[timeeh]

Head is tight, no leaks engine fires fine just not geting full rev band with choke off.

Based on that it's gotta be the carby, do as DHZ said above.

 

[timeeh]

any idea what year lincoln engine it is? Itsa vertical 4 stroke I noticed the new pit bikes are horizontal.

Put up some pics and someone should be able to tell you. As for the carby, soak your jets in cleaner first, then blow out with the compressor.

 

[marty7n]

A needle cleaned out the main jet, but that wasnt the problem it was the jet on the back of the carb down at the float chambe3, got it runin smooth 2ni, all set in time for the weekend, thanks to all for the help and the carb tuning stickys are class helped out alot.long live jap pit bikes.

 

[rotn50]

.long live jap pit bikes.

Long live pitbikes in general:coolthumb: