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Thread: rmk jetting?

  1. #1
    Member BRWNBR's Avatar
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    Default rmk jetting?

    couple questions on rmk jetting. i've got the chart here and it seem like in alaska with the temps you'd need to adjust your jetting every couple months with the change of seasons...is there a good mid jet point that will cover -30 and still work at 30 above?
    its and 800 '03 vertical escape...
    is there anyway to do something to eliminate the jetting?
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    Member Erik in AK's Avatar
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    Jake I can't remember the specific jet size (430 I think) but get an ATACC from Holtzman Engineering and follow the installation and jetting instructions and you'll be good to go.

    I have an 03 700 that's had an ATACC since I bought it new, and I have NEVER messed with jetting. Ever. I've got a shade under 5,000 miles on that sled.

    30 to -30, sea level to 6,000 feet.
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    Moderator AKmud's Avatar
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    If you really want to tinker with it, I'd go with a Dial a jet. I haven't had one personally, but several friends who have used them and swear by them. You might want to invest in a set of EGT's as well if you start messing with jetting though. Last thing you want to do is burn down 80 miles out in the Talkeetnas!
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    Member BRWNBR's Avatar
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    ATACC...where do i find one of those and what do they usually cost you guess?
    sounds much simpler than this jetting stuff...i don't even know what jetting is...lol
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  5. #5

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    ATACC can be seen at www.holtzmaneng.com

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    Member BRWNBR's Avatar
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    thanks kid, i'm checkin' into it...
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    I never needed altitude compensation in Alaska. The Holtzman Tempa Flow provides automatic fuel flow compensation with a less complicated, less expensive system than the ATACC. I've installed and used both. If you really need altitude compensation you need to address the clutching as well. The Tempa Flow can be manually adjusted for altitude compensation if needed.

    GoPro and ERPAC have stocked TempaFlows in the past.

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    Member Dupont Spinner's Avatar
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    Here is a deal on an ATACC....I have installed a bunch of then thru the years and they are a very reliable system. The guy selling this one is a friend who's leaving state. Need help let me know.

    http://www.hardcoresledder.com/forum...arts-sale.html

  9. #9

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    OK someone help me out. Why change your jetting. It seems like you should be able to just set it for the lower altitude and colder temperatures. Then as you climb higher or it gets warmer the machine will just run a little richer, which wouldn't hurt anything, just a little loss in power.

    Do guys really change their jetting as they are riding or as the season warms up.

  10. #10
    Member BRWNBR's Avatar
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    i took the sled to AK motoworks over by valley rental center, Ben Bowers is the shop owner goes to our church and kinda a guru with engines, he's gonna tune 'er up for me and put the atacc on it. i was talking to them about jetting and such and learned that every 1000 feet you climb you loose 3% of your horse power, thats why riding an 800 in utah at 10,000 feet feels like a 550 up here..
    the atacc covers a wider range than a single jet but isn't a onet ime fix all for all temps and elevation changes...
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  11. #11
    Member Erik in AK's Avatar
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    Quote Originally Posted by BRWNBR View Post
    i took the sled to AK motoworks over by valley rental center, Ben Bowers is the shop owner goes to our church and kinda a guru with engines, he's gonna tune 'er up for me and put the atacc on it. i was talking to them about jetting and such and learned that every 1000 feet you climb you loose 3% of your horse power, thats why riding an 800 in utah at 10,000 feet feels like a 550 up here..
    the atacc covers a wider range than a single jet but isn't a one time fix all for all temps and elevation changes...
    Totally correct. The ATACC covers about a 60 degree temp range and 3,000 feet above and below the setting. For most use in Alaska setting the zero, if you will, for 0 degrees at 3,000 feet gives you the numbers I mentioned in the earlier post: -30 to +30 from Sea Level to 6,000 feet, which pretty much covers most of the rideable areas of the state.

    A note about riding in really cold temps (colder then your jetting is set for). Cold air is denser than warm air so it leans out your air/fuel ratio which could lead to a burn down. You can adjust for this by partially obstructing your air intake (a rag laid over the airbox opening works well for this) will richen the air/fuel mixture. As soon as conditions improve you just remove the rag.

    DenaliHunter and I rode back to Cantwell from Maclaren the weekend after Christmas back in 2008. It was a balmy -5 on the trip in but the bottom dropped out that weekend and it was -50 when we left Maclaren. My ATACC equipped machine had a slight lean ping the whole way back. Now I know better...
    If cave men had been trophy hunters the Wooly Mammoth would be alive today

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    [QUOTE=Erik in AK;837297]Totally correct. The ATACC covers about a 60 degree temp range and 3,000 feet above and below the setting. For most use in Alaska setting the zero, if you will, for 0 degrees at 3,000 feet gives you the numbers I mentioned in the earlier post: -30 to +30 from Sea Level to 6,000 feet, which pretty much covers most of the rideable areas of the state.

    A note about riding in really cold temps (colder then your jetting is set for). Cold air is denser than warm air so it leans out your air/fuel ratio which could lead to a burn down. You can adjust for this by partially obstructing your air intake (a rag laid over the airbox opening works well for this) will richen the air/fuel mixture. As soon as conditions improve you just remove the rag.

    QUOTE]

    Erik hit it all right on the money. I did a guys F-5 that was rich when went climbing in Eureka and warm days you almost had to get off and push to get it going if you were high. After the ATACC install it ran like it gained a 100 cc's.

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