I hope someone can help! My sled starts with 2-3 pulls everytime. The idle changes on its own every once in awhile from 1.5-3.0rpms. The idle screw seems to have little effect if i turn it in or out. 0-1/2 throttle it runs great but when i punch the throttle blaahhhhhh. I have to let off the gas or it will keep sputtering. It won't climb over 50 mph. 1989 Yamaha Exciter 570 by the way(don't laugh!) I put in new needle valves, replaced the top end(piston was scored),rebuilt the fuel pump, tried to adjust the needle on the slide to a leaner position with no luck. When I shut off the gas while riding it runs awsome until it runs out of gas. It seems to be flooding out at WOT. Any ideas? It used to do this periodically but now it just does it all the time. Maybe a seal?