engine trouble

[gregy133]

on my 01 rm 125 i just had it rebuilt a few weeks ago and it has ran fine around the yard but when i took it riding this weekend it ran great for about 2 hours then when i stoped for a min and went to take off it stalled out and i couldent start it again and it backfired a few times then i pull started it and it started right up but when i took off it stalled again then i pulled it again and it started up and i reved it up a few times then it started smoking pretty good so i shut it off and brought the truck back to get it

i noticed some oil coming from around the spark plug also

i still have spark and it kicks over just will not fire up and suggestions and what it could be

 

[ellandoh]

first guess would be crank seal

 

[doamono]

a friend of mine had that problem with a jr 50, after he just done the top end. turned out he didnt put the right rings in the right grooves and upside down. it had enough compression to start, but as soon as it warmed up a bit, and everything expanded it just lost compression and died.
your rm would only have one ring but maybe whoever rebuilt it put it in up side down,
do a compression test.

 

[whenfoxforks-ruled]

A leak down test can cover both areas.

 

[_JOE_]

Have you tried a new plug?

 

[gregy133]

i haved a bad crank