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Hi, I'm new to this site, and to working on snowmobiles. I have a '91 Pantera 440 that seems to start fine with the choke on and will idle down and die if the choke is left fully on. When its running and I turn the choke off, it revs back up and then idles back down until it idles so low it dies. If I turn the choke back on half way, it idles back up and then the process repeats. It will stay running when revving the throttle, but boggs down unless you feather the throttle to increase the RPM slowly until the track starts to spin. I hope that makes sense.

I have a carb kit ordered, and I'm pretty certain I can handle cleaning the carbs, but I don't know anything about possible adjustments the carbs may need. Is there much on the carbs to adjust or should i just clean them throw them back on and see what happens? Thanks for your help!
 

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After cleaning/rebuild, you might just check slide height and adjust the idle speed.

Depending on the machine, sometimes I like to make it a bit higher than spec. For example, if the 440 calls for 1800 RPM idle, and clutch engagement is 2500, then I'll take the idle up to 2000-2100. But if it is a utility machine, I like to have the idle as low as it will go without stalling/missing.
 

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I also wrote this up a couple months ago as well for Mikuni Round Carburetors.

When doing a carb cleaning they need to be pulled FROM the sled completely. What I do is this....

I take a white marker pen and mark on the side of it C for clutch or #1 and S for Stator or #2
I then pull the air-box, loosen the clamps on the carb boots and pop out the carbs.
I then slowly unscrew the top of it where the cables are going in and slowly pull out the entire venturi assembly and all. Making sure that nothing falls out. Do make sure if this does happen once the airbox is out put a small box or tub underneath the carbs.
Now I pull the bottom drain hose off to get rid of any fuel into said tub.
Now do this to each carb slowly, also while the cable and venturi's are sitting there doing nothing spray them down with some good carb cleaner CRC or Gumout not cheap Walmart garbage
With each carb off of the sled take them to someplace you can clean them on a nice flat surface
Grab a notebook as well as you will need this for part of the carb cleaning. Also have a tub for the clean parts as well.
Drop the bottom off of it where the 4 screws are, take the gasket off and set it somewhere it will not get ruined otherwise you are looking at buying a new gasket or carb rebuild kit.
Pull the needle/seat off carefully, inspect and make sure you DO NOT lose the clip! Set that off to the side and spray it with some carb cleaner.
Now those floats may or may not come out, ICR on those but those should be ok unless they are cracked.
Now you need to go to the side where the mixture screws are. Make a mental note or write down where each one goes.
For the Idle screw, screw it in to seated and while you do that COUNT how many turns in it took you.... i.e did it take 1.5 turns and it was seated? Regardless of the number right now in the notebook, carb C or S or # 1 or #2 Idle screw needs to be backed out 1.5 turns from seated when re-installing. With that screw out that also needs to be sprayed down with carb cleaner and have a piece of wire possibly run through it as those can get clogged as well.
For the rest of the screws the same instructions apply, count how many turns in each one takes till it is seated, mark it down in your notebook and the type of screw, clean them and set them off to the side with the rest of the clean parts.
Now you can take out the rest of the jets one by one, spraying them down with carb cleaner, cleaning them with a piece of small wire also and set off to side.
Do that with every jet including the needle! One of them will also have a c-clip on it right down in your notebook what position that c-clip was in as it makes a difference.
Once EVERY jet is out and cleaned let them sit while you work on the main body.
Now with NOTHING in the main body of the carb spray it top to down in carb cleaner DO NOT let it sit in carb cleaner for more then a couple minutes.
Take a soft toothbrush and scrub that thing top to bottom, take that small piece of wire and clean each passage thoroughly, take a compressor or canned air and spray it into the carb body several times as all it takes is a very small piece of gunk to make sure nothing is left. Scrub it wherever you see yellow or green as the type of fuel we have these days just gunk's up a carb bad.

Also when done with cleaning the 1st carb put it back together and set off to the side so you are not mixing up or switching parts from one carb to another.

Before putting the carb back together give each jet a quick once over with the wire again and verify by looking in there nothing is left. But it back together in reverse of how you took it apart. If any of the parts are still wet them use the compressor to dry them off.

DO this with EACH CARB!
 

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Discussion Starter #5
After cleaning/rebuild, you might just check slide height and adjust the idle speed.

Depending on the machine, sometimes I like to make it a bit higher than spec. For example, if the 440 calls for 1800 RPM idle, and clutch engagement is 2500, then I'll take the idle up to 2000-2100. But if it is a utility machine, I like to have the idle as low as it will go without stalling/missing.
This is great info, thanks! Do you have any idea how many turns out the pilot air jet should be? Or how many turns out the idle screw should be? I found that one of the old carbs was so gunked up that a bunch of the screws wouldn't even turn. I had already taken them apart by the time I saw your post... Bad decision on my part.
 

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The turns is crucial when doing that. Count how many turns in it takes. But yeah now you are going to have to go to the service manual or wait till KC gets on.
 
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