I second the coil sentiment, one of mine was bad. Also, check the fuel petcock, it is vacuum operated and if the rubber diaphram is not intact the bike will not get fuel in the "run" position. "Prime" will turn the fuel on like a conventional petcock, bypassing the vaccum system. Also, there is a very small passageway in the float bowls that, if blocked, will not allow the bike to idle. Clean these with carb cleaner and make sure you can blow air through them. Clean and blow air through the idle jets. Make sure when you reinstall the carbs the throttle cable is properly hooked up to the carbs. It is easy to hang the cable end when reinstalling it (ask me how I know). If it does not allow the butterflys to shut all the way the bike will never start as the low speed circuit is disabled as the butterflys are opened and the high speed jets take over.