If the motor has been turned over or run with that valve tike that you may have a BENT valve. You will need to pulled the head to get the valve freed up, quite possible replace the piston also.

 

Update: I got the head pulled off, and I did have a bent valve that was stuck open. I found a replacement head on eBay for $34. I have switch the heads and replaced the spark plugs. I double and triple checked the timing when I put the new head on. Engine cranks and runs fine, until I get on the throttle. Loose power after a short rev up. I'm thinking problem in the carburetor, or clogged fuel line?

 

What is compression? Did you PULL the piston to inspect for damage, from when it hit that valve? Was the cam inspected for damage caused by the bent stuck valve? ARe you sure the cam chains got timed correctly? Are you letting it warm-up before getting on the gas?

 

What is compression? I don't have a way to test at them moment. Did you PULL the piston to inspect for damage, from when it hit that valve? I inspected the the head of the piston, and found no damage, but I did not have the appropriate tools to pull the pistion. Was the cam inspected for damage caused by the bent stuck valve? The cam was inspected, and meets specifications. ARe you sure the cam chains got timed correctly? Yes Are you letting it warm-up before getting on the gas? Yes, I have let it idle for ten minuets.

 

If you had the tools to pull the head you had the tools to inspect the piston... What do plugs look like? Is it idling with NO choke? What happens when you apply the choke after warmup? With the new head carbs will need to be adjusted and sync'd. The head did come off the same model and year bike? Was cam chain removed and checked for stretching? Did you FIND that missing tapet nut? Is fuel fresh?

 

Sorry, I should have said that I did not have the tool to reinsert the the piston, so I did not remove it. Yes, it idles with no choke. If i apply the choke after warm up, the engine will rev up and continue to run. The head came of the same model bike. The chain was not removed and checked for stretching. I did find the nut. The fuel is fresh.

 

Sounds like carb to me...mix fuel line antifreeze and some good carb cleaner together, put into gas tank, run for 10 minutes then let sit 2 hours and see if it helped.

 

You stated that when the engine is warm and you give it choke, the engine revs up? Vacuum leak maybe? Especially since you had to pop the carb in order to remove the head.