Please confirm airscrew initial setting - Snowmobile Forum: Your #1 Snowmobile Forum
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post #1 of 4 (permalink) Old 04-09-2019, 08:15 PM Thread Starter
John from Washington
 
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Please confirm airscrew initial setting

I'm pulling together necessary information before I clean my Mikuni VM40 carbs....

I'd like to confirm that I am reading the manual correctly. It appears the initial setting for the VM40 Carb is 2.25 turns out from seating.

Attached is what I snipped from the manual. Did I read correctly? Does anyone have a better initial setting?

Many thanks
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post #2 of 4 (permalink) Old 04-09-2019, 11:06 PM
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Those look like they would be for a Summit with the High Altitude Compensator (HAC) hooked up. Did you count the turns in when you started working on the carbs?

Dan

2018 Skidoo Summit Sport 600
1996 VMax 600 Mountain Max
1994 Indy Lite GT
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post #3 of 4 (permalink) Old 04-10-2019, 09:15 AM
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1.5 is the Norm starting point.

You will also need a Pilot jet screw driver.
Don't try to remove them with the smaller screw driver that happens to fit the tube!
The thickness of the tip is TOO small!
Take a Std 1/4" straight and grind the edges until it fits the tube.
This way you wont strip the slot!

You didn't mention what sled or engine, but on the 800 Rev chassis, inspect the carb boots for cracks!
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post #4 of 4 (permalink) Old 04-10-2019, 10:39 AM Thread Starter
John from Washington
 
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Thank you for the advise. I really like the tip about the screwdriver. 1.5 turns seems to be what I see everywhere, and I surprised to see 2.25 in the manual. That is why I sought a confirmation.

The sled is 1997 SKi-doo Summit 670. 130+ compression on both cylinders, primer (no choke), HAC attached. Starts with 1-2 pulls. I noticed it was dying when I gave it the gas, so I thought a good carb cleaning was in order. I thought best to get some parameters nailed down before I took everything apart. I'll double check those boots


I have a tool modification that I'd like to share -- When pushing in circlips, I took an old stubby screwdriver and cut a square notch in the tip. THis helped be get a better grip on the edge of the circlip when I was pushing on it
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