110cc Loncin running rough when cold

[Tonner]

Hey Guys need a bit of help , I have a 110cc loncin runs like crap when its cold. It use to take only a minute or so after startup to run smoothly, now it takes like 5 minutes. Once it warms up it runs fine. I replaced the plug & discovered it was covered in soot?? & think this may be related to the problem, maybe a sticky or bent valve.

Any Ideas ????????

 

[pitmaster]

just sounds like it needs mixtures adjusted a bit, seeing its only on startup id think its only the idle mixture thats out,

the soot just means its rich, does it pop and backfire while warming up?

but i dont know your engine so cant suggest how you adjust it sorry!

 

[Meko]

If it only runs crap for 5 mins, be patient & wait till it warms up - better for ya engine anyway - do you use the choke? if not - try using it till it warms up

 

[Tonner]

Thanks for the replys

Pitmaster: Nice avatar......No backfiring or popping ...there are 2 screws on the carb, the higher of the two I assume is the idle screw as the engine idle speed increases when screwed in, the lower I assumed was the mixture screw. Does it only affect the idle mixture? After fitting a Uni filter I mucked around a bit with it to get the bike to rev a bit cleaner/faster & it seemed to have the desired affect. This may be the problem however it it is only for Idle mixture, is there a start point, maybe 1.5 turns out I should start from?

If I screw the idle screw in to get the bike to idle cold it revs at about 1800RPM when it is warmed up.

The soot looks dry, not wet as I would have thought, thats why I suspected a bent exhaust valve, compression seems ok though.

Meko : I always let the bike warm up for a couple of minutes, now I have to hold the throttle open a bit or it stalls straight away. I only use the choke for the first cold start & about a quater closed only & open straight after starting. If I leave it on the engine splutters & stalls. If the engine does stall before it is warmed up it is difficult to start again.

Thanks heaps for the help, any thing you think may help further is appreciated.
Thanks Tonner

 

[pitmaster]

thanks!! i like it lol,

there should be 2 screws close together? 1 should have a spring on it, thats the idle speed, the other is the mixture, the mixture one adjusts the mixture up to 1/4 throttle opening and idle, which is why iam pretty sure is the one causing your problem, cause you said once warm its fine correct?

if that was my bike id screw the mixture all the way in and back it out 1.5 turns than see if it runs anybetter, in theory it should be pretty close and be running fairly good at that setting, base setting is usually 1.5-2 turns,

remember only turn it 1/8 turns when your adjusting it once you have a good base setting,

dry sooty plug is perfect for a rich running engine, doubt very much its mechanical problem,

Cheers

 

[cass38a]

What type of carby is it?

 

[Tonner]

Thanks Pitmaster I will give it a go & let you know how it went.

Cheers

 

[Tonner]

G-day cass38a, at a guess it looks like a chinese copy of a mikuni carb.