I rebuilt a 2005 300ex, I got it started and the bike lost compression? Any ideas would be GREATLY appreciated

 

you sure it lost compression? take the cap off the side of the motor to see the crank bolt.. try cranking it and see if the bolt turns.. i've thought that a couple times and the starter clutch just sheared the key off.

 

Thanks for the input. I figured out what happened. A neighbor tried helping me get this started after a rebuild, he shot starting fluid in the air box to get it to fire, the starting fluid washed all the oil out of the jug which made the rings not seat which caused my compression loss. NEVER use starting fluid!!!! I guess it,s nice to have friends that drag race and build motors