I recently brought a 1986 flat deck sj413 and after countless hours of work I finally got it going, but now after rebuilding the carb the engine idles fine and drives fine at lower rpm but after high revs when returning back to idle speed it just cuts out, after that it refuses to start or will start but cuts out a couple of seconds later. Ive checked for vaccum leaks and found nothing. Any help would really be appreciated 😊