i rebuilt the top end about 2 weeks ago been running fine, breaking it in then i decided to take it on a short ride, well all well and good till i get back to the street it just loses power and shuts off , wont start back up, never went past half throttle, iv change the oil 3 times so far and one of the times was before i went for the quick ride,

 

If you're talking about changing the transmission oil,that shouldn't have anything to do with the top end. Did you have the cylinder bored to the next oversize that would clean it up,plus did you check or replace the rod,lower rod bearing and crank bearings or just do the top end only? Dirt Cheap Honda & Arctic Cat OEM Parts & Accessories – Cycle Parts Outlet

 

yes i had the cylinder bored out to .20 overs rod bearings were replaced .all bottom end bearings were replaced , i put a new bigger 34mm carb on , my plug is a blackish color
bike has everything stock other then the cylinder bore at the moment