yx 140 help

[rockstar energy]

i have a pit pro 140xr with a yx140 and a mikuni carby. the other day it just started backfiring and idling low. when we turn the idling up it goes back down eventualy and then if you dont rev it it will stall. it also takes lots of kicks to get it started ( which when it didnt backfire and didnt play up it would start first or second kick ) but it has lots of compression because sometimes it kicks back. we only got the valves done the other day. Can anyone help me solve this proplem.
Thanks

 

[qwerty123]

Ive had the exact same problem but never solved it

idle is revving up then down to a stall cant idle properly

5 minutes later it stopped doing it and it all went back to normal

what is it?

 

[no_crf50_here]

basics - Adjust valves & Check for air leaks after the carby.

 

[rockstar energy]

we got the valves done the other day so it cant be them.

 

[SnItChY]

we got the valves done the other day so it cant be them.

seems there is your answer then , have been done incorrect or have moved ,more the later as your bike was obviously running find when it was adjusted ?

 

[skruba]

****ty carby maybe???? not a grat seal on manifold....

 

[DvDRip]

yea it really sounds like a leaky manifold (intake OR exhaust) or maybe low float level.
I woulda said valves but seems you've got them checked, I would set them again just in case

 

[sean01]

check yr fuel cap breather.. re-check your tappets.. clean the carb and air filter

 

[rockstar energy]

ok thanks for that ill go and try that

 

[rockstar energy]

what is the valve clearance for a yx140?

 

[DvDRip]

0.003 intake ... 0.004 exhaust
and that's thou, so don't get confused, it's NOT 0.03 / 0.04

 

[bournie]

I used to have this problem with my pitpro, you need to tune the carbies float level(thats what I did)

 

[Mxrider23]

i also had this problem and changed every thing and still couldnt start it,.check the port were the manilfold bolts onto the engine and inside you might have some grease like sort of sh!t, took me foverever to figure it out , hope you fix it

 

[rockstar energy]

thanks for all your help guys i found out that the manifold gasket half was missing.
thanks

 

[beccsptyltd]

.003 i think

 

[no_crf50_here]

Check for air leaks after the carby.

Pete for the win... glad to hear you have it sorted