yz250 compresstion and starting help

[nwwrestler171]

i have a 1986 yz just rebuild maybe 5 hours ago maybe up to 8 and it only has 87 pis for compression and all it does is backfire when i kick it afterr every 3rd kick what could be the promblem?

derek

 

[tcuda499]

well thats pretty low compression.what was done on the rebuild? top end or total rebuild?

 

[nwwrestler171]

i did a total rebuild with new trans and piston crank and everything

 

[DLHamblin]

i did a total rebuild with new trans and piston crank and everything

What shape was (is) the cylinder in? What type preperation was done to it? Is it still within limits?

 

[jcarautos1]

Did you replace the plug? How old is the gas? Did you make sure the magnito was clean and tightened up?

 

[nwwrestler171]

the jug was just bored and ya i hope it only had 6 hours on it and yes i tried 5 new plugs it would like back fire once and that was the end of that plug and i just put the gas in there like a week an a half ago and yea i looked that all over

 

[MXer666]

now stupid question here, but its been done before. when you bored the cylinder, did you buy the appropriate size piston?