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Thread: High Altitude Adjustments?

  1. #1
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    Default High Altitude Adjustments?

    I have a Yamaha MM600 that I have typically ride between 500-2000ft around Fairbanks. This weekend, I will be at 3-4000ft. My question is, what kind of performance changes can I expect if I don't make any adjustments? Does 3000ft really make much of a difference as far as performance, plug fouling, etc goes? The operators manual says the drive chain gears and clutch should be adjusted above 3000ft along with all the carburetor adjustments. I am not an expert in sled maintenance and the thing runs great now so I don't want to screw it up. Also, I don't want to pay to have someone do it just to adjust it back after the weekend. Thanks for any replies.

  2. #2

    Default altitude

    i would premix my gas

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    I usually change my jets and primary spring. You can do that if you want top performance.

    If you don't do anything the engine will run richer which could create a bog and loss of throttle response. Your clutching wont allow the engine to rev as high (maybe 2-300 rpm less).

    Kinda depends on what you are doing. Going to be climbing to 5-6000, then you're going to loose even more. If you're just going to run the trails then I probably wouldn't worry about it.

    But some machines respond differently. You might not notice much of a difference depending on how you ride.

    You also need to look at what the temperatures are going to do.

    I wouldn't pay someone to do it then have to pay them to undo it. Bare minimum would be jetting. On most machines it is pretty simple, I've never changed jets on a MM before.

    If you don't feel comfortable doing anything then don't. Your machine will still run, just not as well as the lower altitudes. Maybe bring a couple spare spark plugs.

    I'm not sure why bboy said to premix, never heard of doing that for this situation.

  4. #4
    Member Erik in AK's Avatar
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    For the longer term you may want to consider investing in an altitude compensator. I had one put on my 03 RMK when I bought it and it works as advertised. I would assume Yamaha or the aftermarket has them for your sled.

  5. #5

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    I agree with everything kgrant said,

    Keep it simple. I have run 700 Mmax’es in Cantwell/Hoo-Doos for years without changing a thing.

    You will notice a difference in the spring though (warmer temps).

    Your 600 may act a little diff. than the 700. Your running 2 carbs instead of 3. I never was a big fan of the 600 Smart-carb system either.

    Run it as is this weekend. No chance of it running too lean. After the motor is at operating temps. you may have to open the throttle a little each time you start it.

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    The altitude variations that most of us will see here don't justify too much fiddling, unless fiddling is what you like to do. Temperatures are a different story.

    I'm a big fan of Holtzmann Engineering's Tempa Flow. Those little devices make a very big improvement. -20* at sea level to +50* in the mountains at Arctic Man, my sleds run great with no adjustments. I tried their ATACC once but didn't find any advantage over the Tempa Flow, and the ATACC is more complicated. I prefer simple.

  7. #7
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    Default Thanks

    Thanks for all the replies. I will probably just leave it as is. The last time I rode at any altitude, was last year in the White Mountains (about 3000 ft). The sled ran terrible and guzzled gas, even after changing the plugs. It was the first ride of the season and I was pretty sure I had some bad gas left over from the previous season. Hopefully, it wasn't the altitude.

  8. #8
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    If it ran crappy last time it will probably run crappy this time. I have never had any gas go bad, but I'm sure it happens. But I think with our mild climate and short summers it doesn't happen much.

    I would get a jet chart and jet it for the altitude and temperature you'll be riding at.

    If you do have it jetted for warm temps, and it gets cold (like night time in the mountains) just stuff a rag in the air intake. With the rag you're restricting airflow, which will cause it to run richer. A little learning curve to find out how much it takes. Just watch you're plugs. The rag was easy to use on the older polaris sleds, don't know about any of the new one or other models.

    Or look into getting a compinsator, I've never messed with those though.

  9. #9

    Default premix

    if you want ot keep your oil tank and injector just use a hose clamp to stop them. im about to take mine out. its nice becuase you can change your gas/oil mixture when ever you need to. if u start heading up the mountians add a little more oil. its simple lighter and works well

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