Usually this means you have an air leak somewhere or plugged jets in the carbs. If timing is advanced too far and its too warm outside it could burn down also. First check for air leaks (seals, gaskets) and clean carbs thoroughly.
i cleand the carbs verry thouroly. im not eactly sure how to set the timing? the rotary valve seems to have a little bit of wear in the middle, could this be the problem? what is the correct angle for setting the timing on the rotary? what are the correct size jets
` Talk to a skidoo guy, shop. I use to be into the rotaries but it's been too long. I do remember thinking just before btc the rotary would just be starting to close the transfer port with the valve. A little rub marks on the valves leading edges are normal. I think your on the right track ,verify the stock main settings, I also recall the pto side being richer by one step. Try your post on amsnow.com , some amazing help there.
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