broke a valve a couple weeks ago and after a new head, valves, top end etc. I took it for a spin only to have the coolant leak out and it ran hot. Took it back down and found a blown head gasket. replaced the gasket checked everything over and got it back running but found it to be a little sluggish. after a few rides it started popping and stalled. Took it down again and I can't find anything visibly wrong and it runs well on idle but stalls as soon as I hit the throttle. no adjustments were made to anything while I had it down other than the valve clearance which is in spec. and ideas??????