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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?
 

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What type of carbs, when you tore the carbs down did you make sure all the ports (openings) were clean with carb cleaner and then use air compressor to spray? Sounds like you may have a opening not fully cleaned.
Or when you calibrated the carb cables. Did you do them off the engine? Stearing straight, carbs laid as flat and straight as possible?? then when you adjusted them give gas and relase a couple of times, then check to see if they are still the same?
Also how are the full filters or filter? and the hoses being that old. and the vaccum hose for the fuel pump??

hope some of the ideas help, not that you may not of thought of most of these.
 

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Why laff I used to ride the Exciters and worked on alot of them also
First off whats the compression on both cylinders
(using a compression guage and pulling the motor over 7 pulls with the throttle wide open)
Your compression should be no lower than 125psi
If the compession is good whats your jets sizes?????
Is it piped????
Does it have the aftermarket direct oil injection kit ?????
Do you leave the carb heater on at all times???
I have the specs for all the above
 
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