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Discussion Starter · #1 ·
i have a 77 cheetah with the 500cc twin spirit motor. and it runs, sorta. when it is running it lacks power, has no snap at all. when it gets warm it barley as enough to spin the belt. it did have old gas in it, put fresh in. didn't make much a difference. i think its a carb issue, but i haven't a clue with adjusting carbs. also the exhaust has a big hole were the header and expansion pipe come together. please help.
 

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has this machine been sitting for a while if so deffinatly clean the carb. i cant help you much with the adjusting part sorry but if you take the carb apart before removing any adjusting screw count how many turns it takes to seat the screw then just put it back to that setting when finished cleaning. most will have an idle air adjustment for fine tuning idle and low end performance make note of how many turns it is out if the pilot jet is correct between 1 and 2 turns out will generally be were it is when adjusted correctly. if you find its out much more than that you need to check the spring under the screw that keeps it from backing out and/or the size of the pilot jet. the exhaust problem deffinetly needs to be addressed. a 2 stroke relies heavily on the expansion effect of the exhaust system to scavange exhaust from the cylinder. with out a properly functioning exhaust the spent gasses have a hard time escaping the cylinder good luck let me know what you find
 

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Discussion Starter · #3 ·
i'm not for sure if its been sitting vary long as i just bought it lss than a week ago. but just from the smell of the gas it had i would say it has been. but thank you for the info. i will clean the carb. i do know how to do that. as for the adjustment screws. bone head me made and attempt to adjust them. but i will use what you told me for a starting point when i put the carb back on. the exhaust i plan on getting a new or at least a still good used one. but yeah i do know that the expansion chamber is a vital part for proper two stroke operation, just wasn't to sure on how vital. but again thank you
 

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Air screw is set at 1 1/4 turn, (air screw = the small one) Throttle stop 1 1/2 turns, jet needle is second slot from the top. These are all per the 1978 Factory manual on the cheetah 5000 with the mikuni 34 carb. I would assume yours is the same. Spirit 500 motor
 

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Discussion Starter · #5 ·
thanx, i have gotten a repair manual for it, arctic cat made some changes in 78 its even noted in the manual, for 77 its one turn out for both screws, who knows it might like the 1/4 and 1/2 (respectively) more out. but i found my main problem to be a broken choke lever. i currently start it by adjusting the choke to open then screw it back down. will be fixed once i get the part. gonna try turning the screws out that lil bit more to see how she likes it. regardless thanks for the info.
 
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