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Like many other members of this forum I too am experiencing a bit of trouble with my sled (95' XCR 600) at idle.

Two of the three cylinders were fouling pretty badly, the third was fine. So I get out my trusty shop manual that I just bought from Crappy Tire and begin making adjustments.

Turn the air screw out 1/4 turn and no difference, 1/4 turn more and nothing, 1/4 turn more and things are getting progressively worse??
Plugs are now soaked..., Incidently, this was done over the course of a week or so and several sets of plugs as well. The air screw was now out 2 3/4 turns so I know something is wrong.

Now I am really confused so I go to the Mikuni site to try to research this out. Now I think I have VM38's as stock carbs, Yes?

I come across one page that says to lean your mixture at idle to 1/4 throttle you need to turn the screw out or counterclockwise...HOWEVER,
If your air screw is at the front of the carb the procedure is reversed and you must turn the air screw in or clockwise in order to lean it out!

So, out I go to the garage, grab a fresh set of plugs and reset the air screw. I turn it in all the way so it gently seats than back off one turn (a full 1 1/2 turns in from were I started).

Voila, It is now idling clean and plugs are dry...

My question?... For my own benefit can someone explain to me why the shop manual and owners manual tells me to turn the air screw out to lean it out but by doing so, does the exact oppisite

Thanks!!
 

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Same with my '92 Ski-Doo Mach 1 guide...WAY off...don't know why, jetting??
 

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More often than not some crud will get stuck in theair passage that the screw regulates. Just like the shop manual states screw it out and it leans it out. Whatever may have been plugging the hole might have worked it's way out and you changing the plugs probably had a bigger impact on your sled.
 

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I come across one page that says to lean your mixture at idle to 1/4 throttle you need to turn the screw out or counterclockwise...HOWEVER,
If your air screw is at the front of the carb the procedure is reversed and you must turn the air screw in or clockwise in order to lean it out!
I think what you were talking about by the front screw is the idle adjustment screw. It is the bigger screw you can turn by hand. I guess you could say that turning it in (clockwise) leans it out but it really just raises the throttle valve to let more air flow enter.

I agree with the other guys that turning the smaller screw in the back (pilot air screw) counterclockwise leans it out.
 
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