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Discussion Starter · #1 ·
Looking for help to get an old '85 Polarid Indy Trail 488 running again. Started it up a couple of weeks ago and it ran for about 10 minuted before it blew one head gasket. Replaced it and noticed that all the head bolts were quite loose. Torqued them to 18 ft-lb. Fired it up again but can't get any real RPM out of it. Engine boggs down when you throttle up and you have to feather it to get it to come up to RPM. Left to idle it will stall right out. Any suggestions on how to setup the carbs? i noticed very different settings on the two needles when I looked.

Also, I'm replacing the air intake which is all busted up and putting individual K&N filters right on the crabs.

Any help is appreciated - kids are buggin me to get the sled running now that we got lots of snow...
 

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Sounds like it has been sitting a while, pulle the carbs off and clean them real good, sound like the pilot jets are varnished up, will cause the stalls at idle problem
 

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Discussion Starter · #3 ·
Probably a good idea... but then after i get them back in, how do i adjust the needle valve? There is a large adjustment screw on one side - what does that adjust? I admit I don't know much about carbs...
Thanks.
 

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The large knob o the side of each carb is the idle adjuster. There is also a small slotted screw on the same side closer to the intake side of the carb that is slightly angled down. That is your air mixture screw. screw that in until it seats lightly then screw it out 1 full turn.

When you disassemble the carbs make sure you get all of the orifices blown out. Make sure the floats move freely and put it all back together. As long as you have good fuel supply, spark and compression it should fire up.

If the sled has been sitting for a long period of time you should drain the fuel from the tank and rinse it out with new gas.
 

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Discussion Starter · #5 ·
ok, just dissasembled and cleaned out the carbs, put them back in and got it to run - sort of. At first I turned the air mix screw all the way in and backed it out 1 turn. I needed chocke to start the engine and it would run for about 10-20 seconds before it died. feathering the throttle kept it running. I found that I had to turn the air mix screw all the way in to keep it running on its own at idle (this is with the idle screws all the way in - for max idle, I presume). It idles around 3000RPM.

When I try to go the engine boggs down at first and is real sluggish. After a second or two I can get it up to speed and it seems to run fine at speed. Lots of power and responsive.

I did use fresh fuel.
 

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Thanks. On that note I have a 86 polaris 488. This thing is a moose to start. Could it be needle position. Air fuel screw about 1 turn idles about 1900. 2 grand super hard to start though. Thoughts
 

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The needle jet/jet needle mostly meters fuel from the main jet while the carbs are from 1/4 throttle to 3/4 throttle. At about 3/4 throttle, the needle is pretty much out of the way and the main jet is what is metering. Starting and idle problems are usually caused by the pilot jet and the air and fuel passages to the pilot jet. Those are all small and are easily gummed up with varnish from evaporating gasoline.

Hard starting with an engine in good mechanical condition is usually caused by pilot jets that are clogged or choke plungers that are stuck in the bore or are not seating properly. That's why Coolhand suggests cleaning, it should be a ritual for all snowmobile carbs prior to the season.
 

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I would suggest that you buy a manual for your year of sled. Got mine off Amazon. Tells how to do everything on your sled.

Sent from my SM-G955U using Tapatalk
 
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