Okay, so I've been trying to get all the problems fixed with a 1995 XT600 that I bought last fall. The bike was in bad shape, and I don't know its history. I've bought many new parts, and as I browse for carb parts, I realize I don't have a checkvalve that is shown on the exploded diagram of the carb. The checkvalve goes on the "air vent pipe" going to secondary carb: PIPE,AIRVENT 3TD-14197-10-00 (replaces 3TD-14197-00-00) Can this missing checkvalve be the source of some my high end performance problems? Currently I'm having to adjust the sync between the carbs such that the secondary does not open until the primary is full open; else the engine dies. Thanks for any help. Best Regards, John Hermann