i just recently put a new head gasket on my 84 250 and now the thing will start on the first kick everytime but once it's been running for about a minute or two it gets a knock in the cylinder. any suggestions would be greatly appreciated.

 

well it could be your rod knocking and thats not good or the bearings are worn out on the crankshaft

 

If it has not knocked before sounds like the head gasket is too small. and your piston is hittin your head.