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Discussion Starter #1
I recently picked up a free 1989 ski doo formula mx . I drained the gas and replaced with fresh stuff. Took apart the carbs and did a general cleaning of them but now I have have gas running out of the line coming from the side of the carb near the top. I am new to ski doo sleds and how things work on them. I work more on the vintage stuff. Any advice and or diagrams of the carb set up and possible reasons for my issue would be greatly appreciated.

Thanks

Charlie
 

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Vintage Sled Pilot
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The tube I believe your speaking of is the vent line. If you have gas running out of them, I would believe that you have a leaking needle and seat (not sealing) or the float in the carb is not floating. I would start there.
 

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Discussion Starter #4
Thanks for the help. Any one have a diagram of the carbs so I now what to look for?
Thanks,
Charlie
 

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Vintage Sled Pilot
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Here is a Mikuni tuning manual and a cut away diagram at this link http://www.mikunipower.com/Manuals/VM_Manual.pdf I hope this helps... From this guide, I have cleaned and calibrated 8 carbs this year. All of these sleds now idle like gentlemen and scream like .... well, you get my drift. If any of you know how to upload this link to the sticky threads, please do so!:thumbsup:
 

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Discussion Starter #6
Update:
I cleaned and replaced carbs. New fuel line and new fuel pump installed.
Problem:
I prime the motor to get it started than it runs only when I continue to prime it. It also runs almost wide open. When I try the throttle it just bogs the motor down. If left alone, it will run for about 10 seconds and than just die as if someone hit the kill switch.

Thoughts, ideas, suggestions?

Thanks
Charlie
 

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Vintage Sled Pilot
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Sounds once again like it is not getting fuel through the pilot jets. Is the idle mix screw set at 1.25 turns out? Also check the carb to engine boots for cracks, that would cause the high speed screaming. Did you run a wire through ALL the passages of the carb? This step is a MUST! sorry to sound like we're beating a dead horse, but it is definately a fuel delivery problem.
 

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i have an arctic cat jag 440 1988 and im having the same problem i cleaned the carb and put in fresh gas and it bogs everytime i give it throttle but i idles fine
 

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Discussion Starter #9
Update:
Cleaned carbs
Checked boots from carb to motor.

Thing idles at like 3500 rpm and smokes like a chimney.
It does not idle down and it bogs when you hit the gas but clears out and winds up.

HELP

Charlie
 

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Vintage Sled Pilot
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To adjust the idle down, find the screw on the side of the carb that has a spring wrapped around it. start by turning it out (counterclockwise) by a 1/4 turn at a time. And make sure you adjust both carbs the same amount. I would actually turn the screws, (with the springs) fully in, clockwise, and count how many turns it takes. Then I would back them both out (counterclockwise) the same number of turns. This set's the slide in both carbs to the same position. Then I would begin to turn them out (counterclockwise) by the 1/4 turns until you acheive a 1500 to 1800 rpm idle. Just make sure that the screws on both carbs are turned out the same number of turns. Hope this helps.
 

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Discussion Starter #13
Any idea where would be a good place to start with the number of turns. I have had the carbs apart so I do not know/remember where they were set at.

Thanks,
Charlie
 

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Vintage Sled Pilot
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I would start at 2.5 turns out. Make sure to set the parking brake also, runaway sleds are no fun!:laugh:
 

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Discussion Starter #15
Thanks for the info.....things are going in the right direction but I noticed that one of the carbs is puking gas out of the vent line. Not all the time but it does change how the motor is running until it pukes gas out. I am new to mikuni carbs so I don't what type I am looking at or where to get parts.

Charlie
 

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Vintage Sled Pilot
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The carb that is puking fuel out of the vent has a bad needle and seat. You'll have pullit and remove the bowl. Remove the needle and see if the rubber is all chewed up. It also may not be sliding freely in the seat. Clean both the needle and seat really well with carb cleaner. Take your time and work the needle and seat with the bowl off to make sure nothing is hanging up. Good luck and happy new year!
 
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