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I'm new to snowmobiles and recently purchased a 1995 Arctic Cat Cougar 550. I live in the mountains of Alberta at about 4500 feet elevation. The sled runs very well at this altitude, but I tried going higher and at about 5500 feet the engine bogged down. I (foolishly) tried to adjust the thumb screw on the side of each carburator thinking that it was just getting too much gas with the thinner atmosphere. This didn't seem to help much so I went back down the mountain. I will usually operate the sled at around 4500 to 5000 feet, but will sometimes go as high as 7000 feet or so.

I'm wondering if someone could tell me how to reset the screws I messed with to get them back to the correct (before I messed with it!) setting. Also, any advice on how to adjust the carb to handle the higher elevations would be greatly appreciated.

Thanks!
 

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Snowmobile carbs use fixed jets. The big brass screws should be the idle speed ajustment screws, so just get them equal and the sled running smoothly and all should fine. With fixed jetting you have a couple of variables to take into consideration. The fuel requirements of the engine are based on the air density, amount of oxygen in the air, so that depends on elevation and also on air temperature, as well as barometric conditions. The engine loses power when it is over fueled, but when it is slightly under fueled it will generate too much combustion heat and melt the pistons, so you want to be aware of that. If the carbs are properly set up then you only need to change the main jets for changes in air temperature and elevation. Another impact of elevation is that engine power drops as elevations increase and it can require changes to clutch calibration, but clutch for where you ride most often. Holtzman Engineering makes an automatic compensator that will automatically adjust a craburetor's fuel delivery for both elevation and temperature changes, or you can do it manually by changing main jets based on conditiond and demands of your engine. Main jets are cheap, but if you pick the wrong ones for the conditons you are in, then you may have to pay for a new top end on your engine.
 
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