Mercury Snowmobiles Discussion Board

by **Mike Horrigan** » Sat Mar 07, 2009 7:48 pm

Carbs just rebuilt

Running on two cylinders at medium or high speed
Bogs on low speed
Will not idle without a little throttle applied
Mag side carb spitting fuel out of the overflow tubes.
How many turn should the idle and the low speed screws be set at initially?

by **SnoTwister340** » Sat Mar 07, 2009 8:59 pm

whats the sled? Sno Twister/Trail Twister??? 250/340/440?

by **merc-eric** » Sat Mar 07, 2009 9:35 pm

I need the same info for the low speed air screws for my 76 440 trail twister so hopefully we get an answer!

by **Mike Horrigan** » Sat Mar 07, 2009 10:35 pm

1975 Sno Twister 340 with 34/rs carbs

by **Drivebelt** » Sun Mar 08, 2009 12:20 pm

Did you make sure to clean the pilot jets? Sometimes they get missed, and if plugged, will cause the idling problems. Initial setting for the air screws is 1 1/2 turns out. Make sure carb slides are moving in sync, turn idle screws in until they just touch the slides then turn 3 turns. Jet needle clip should be in the fourth slot from the top. Once the engine warms up you can adjust the air screws in or out to get the best idle.

by **Mike Horrigan** » Sat Apr 18, 2009 10:52 am

I did forget the pilot jets, plugged solid. Running quite good now.
Thanks for the help

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Tuning a Mikuni (Help!)75 340 Sno Twister

Tuning a Mikuni (Help!)75 340 Sno Twister

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