Just finished rebuilding and tuning my 1997 MXZ 670. Today for the second time it died under hard acceleration. It quits after about 7 or so seconds at WOT, otherwise it runs absolutely fine. It takes a good hour of cool down and then it slowly starts to fire and run. It’ll run after that….like a sewing machine. I can’t figure out what’s going on, it has good spark and all kinds of fuel. It will not fire till it cools right down. Ideas? I’m lost.