my 74 cheetah 340 has been acting up lately. It is a kawasaki 340 twin with the walbro carb on it. If i shut it off after riding for like 45 mins to an hour, and i come back to start it it will fire, then quit. After this no matter what i do it wont run. i can even spray ether in the carb and the plugs and it still wont fire. If i disconnect the impulse line from the carb, it will pop and fire until it stays running then if i plug that line back in it is fine. when i pull the plugs out when this is happening the plugs are bone dry, and they are a good brown color too. is this vapor lock? is my carb messed? thanks btw this only happens every once in a while.