Upjetting causing 4 stroking at full throttle to re-appear

Michael80chinadoll

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So i got a mz65 pipe and rid it for a while and it wasnt 4 stroking like it was before i had the mz65.Lots of people have said you need to get a bigger main jet so i did and its a #72 and now when im full throttle its 4 stroking again so what do i do?
 
Or go back to your original jet which you say was not 4 stroking like before after you changed the pipe over.

A certain amount of 4 stroking is normal and desirable for lubrication and cooling purposes, especially so if the motor is still being broken in.
 
Or go back to your original jet which you say was not 4 stroking like before after you changed the pipe over.

A certain amount of 4 stroking is normal and desirable for lubrication and cooling purposes, especially so if the motor is still being broken in.
Yeah its broke in by now and it was very badly 4 stroking but it was definitely running lean with stock jet because when i checked the spark plug it was greyish in colour
 
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