I was in a hurry when I posted my question...sorry. The engine has been rebuilt with fresh bore/hone and .040" over Wiseco pistons. The carbs are stock with TORS caps removed. I'm running a clean/freshly-oiled K&N air filter, BUT in order to get the engine drawing fuel, I have to remove the air filter and cover the carb intakes with my hand. Then, with the carb intakes covered, when I kick it, fuel premix saturates the carb throats and the engine starts. The quad then idles great and runs awesome. If I shut it down and immediately try to restart it, it starts fine. But if I let it cool down and try to start it...nothing. Then I have to remove the air filter and start the whole process over again. The choke doesn't seem to have any effect whatsoever. Any advice???