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my son bought a 87 arctic cat 5000 , sled starts and runs will rev up after fethering the throttle , but a lot of the times it will backfire , out the exhaust , is better after it warms up but this isnt going to fly when snow hits , i want to help him fix it hope nothing major i had a back fusion 1 month ago so i am limited on helping a lot changed the plugs had a friend go through the carbs not sure if he set the air screw right idles fine lost at this tim any ideas would be great , sled seems to be running real rich , may just be me i havent had a sled in 15 years so i may be way off
 

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I am Spartacus
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Sounds like the carbs weren't either cleaned or set correctly. There are 2 screws on the carbs to know about: The large ones on the side are the idle, the small angled ones toward the top/side are the air bleeds. Those might need to be adjusted. Turn the mall the way in and then 1 1/2 turns out. See what that does. If it's still running badly, go 1/4 turn in on each. If it gets worse, go the other way. If these screws have no effect, there's another problem, either with the carbs, or fuel pump, etc.
 

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Mine did that too, adjust like SEG said and make sure the carbs are in sinc. SEG, how you sinc your triple? 2stroke doesnt seem like 4stroke with sincing, can use mercury sinc on them. Can sinc 4 cylinders and twins, even single cylinders...lol, but cant finger out the triple 2stroke. I know the adjust so all open evenly but is that enough?
 

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I vacuum sync them, pretty easy really. I first use 3 same size drill bits in the carb throats to see if they all open/close at the same times. Then vacuum sync them while it's running.
 

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HMMM, ill have to try that. One guy told me to use 1/8 bits but that puts it into 4000 on the tach. I tried the vac last time but had wild readings due to the work on the engine. Thanks SEG, i will try that with fresh topend, tryin to stay ahead of buddies F7 even though hes reeding and clutching it. He hates the tank keeping with his ditch pickle...LOL
 

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The biggest thing the drill bits do is to make sure there is slack on the cable and that the idle screws are actually doing their job by letting the slides rest on them. Then you use the vacuum sync to get them all idling together.
 

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See these guys so called "master tech" on Doo's said to put in the 1/8 bits and adjust the idle screws till they move then back off a 1/4 turn. Im no master by any means, but how can you be a master tech on ski-doo when you never rode period. Harley is the same way, if you read their manuals and assemble their product, as they would say, you muff up your engine and doin the trans by the book you might as well buy a new trans case. You got to be out in the field and try your theory not think and say its ok until theres enough complaints to call a recall...lol
 
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