Motorcycle Repair: honda xr 350 running poorly, honda xr 350, camshaft timing

Question
hey guys. i got a 1984 honda xr350. Bought it last week and it burnt oil so i brought it in had the valves re-done and all new gaskets and i finished putting the head/carbs, plastics etc together and i fire er up and she fires up 1st or second kick. But when i give er gas when the rpms start coming down she starts popping really loud then a big backfire and it only does it when i let off the throttle. what should i do?? let me no asap please reply to my email i have given abouve. thanks so much  

Answer
Hi Mike,

May have the valve timing off a point or two. Recheck walve/camshaft timing. Have another person check the timing- they may find something you've overlooked.

Perform a cylinder compression check. Follow with a leak-down test. These tests will indicate problems if any.

Respectfully,
Mark Shively