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Discussion Starter #1
Looking to go to Revelstoke for our first mountain trip. We have a variety of sleds that are not set up for the mountains:
2015 Ski-doo 600 Renegade (carb)
2010 Arctic Cat Crossfire 600 EFI
2008 Ski-doo MXZ 800 (carb)
2007 Polaris RMK 600 HO 155 (carb)

What does it take to set these up for the mountains? Surprisingly, I couldn't ever find a youtube video on this.
 

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The RMK came stock set up for the mountains. So look at the stock spring/helix/weight recommendations for the stock sled and change to that if necessary. Jet the carbs for temp and elevation.

For the other sleds, compare the jetting and clutching for similar mountain sleds with the same engine made by the manufacturer. That should get you in the ball park.

Have fun!
 

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Discussion Starter #3
Thanks, I have a few more questions:\
Jetting:
1. How do I know what size jet to put it?
2. Do I only need to replace the main jet?
3. Do you have to get the carbs right off the machines...how big of a job is it to change the jet? Can this be done on the hill or realistically in the shop?
4. What if I don't change the jets? Will it just be a performance issue or can I wreck something? If performance, how bad will it be? I'm not out to highmark anyone...just have some fun boondocking in the powder.

Clutches
1. I know how to adjust he top end on the ski-doos, but rpm should I target?
2. How do I determine if I need to adjust weights or springs? How do I know what weight ane springs to replace them with?
3. As above, what are risks if I do nothing. Will I still enjoy the ride?

Thanks for the help!
 

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For jetting, there are jetting charts that manufacturers have developed to keep the jetting safe. Jetting needs to change to a smaller jet as you go up in elevation, larger as you go down in elevation. The same is true for temperature; larger jets are needed for colder temps, smaller for warm.

Usually, only the main jet will need to be changed. The pilot jet may be the same. Some carbs have an air jet or other jets, as well..

The easiest way to change the jets is with the carb off the machine. You have to pull the float bowl to access the main jet, which will prove difficult while the carb is on the engine. It can be done in the field, but you will be dumping gas from the floats and the chance of losing small parts is a lot greater. The closer to the "edge" you jet, the more often you have to change. I would figure the lowest elevation and lowest temperature you could encounter and jet for that. That way, you will be safe. Rich jetting will rob you of power, sometimes to the point of not even being to move the sled. Lean jetting burns hot and can melt holes in your pistons. If you don't change jets and are set up for 500 feet, and ride at 5000, your air/fuel will be so rich you may not be able to move the sled forward.

If you ride in a really varied area that has thousands of feet of vertical rise, jetting can be a problem; you want to keep as much performance as you can, as an engine loses about 3% of power simply because of elevation rise (unless you have a turbo!) That's one of the reasons EFI is so popular, as it compensates for the elevation and temperature changes and keeps the engine at peak performance, regardless.

Clutching is the same. Each manufacturer has recommendations for low and high altitude. If you set up for low and ride at high, there won't be enough power available to run the weights (remember, 3% loss per 1000 feet.) You usually have to run lighter weights to keep the RPM in the power band, as well as change the ramp angle to maintain proper backshifting.

Regardless of the elevation, the whole point in clutching is to keep the engine in the power band and not over-rev or under-rev. Springs, weights, helix ramp angle all play a part. The dealer or a good mechanic should have advice for you. So may the shops in the area you are riding; they know what works for their area. That may prove to be a bit late unless you can ID a good shop and call beforehand...

Good luck, and have a blast!
 
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