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  1. #1

    Tunning a Dean 1050 with a coffman pipe.

    Hey guys,

    I am starting to build my 1050 motor for my 2000XP.

    This motor will be run on 93-94 OCT and will be used for rec use.
    I have a few questions to get me started in the right direction that I would like some help with.

    I am using Crash's old 1050 motor. Running stock carbs for now.


    http://www.pwctoday.com/showthread.p...highlight=1050

    Deans team super stock motor=
    This includes.....
    NEW crank w/ 1 moto,trued and welded.

    rebuilt / new counter balance
    ported cases
    ported cylinder
    miller new style head with 49cc domes
    rave blades (2)
    NEW flat top pistons w/ 1 moto,91.89mm


    1. Do I need to reprogram my timing for this motor? (coffman pipe)

    2. What base gasket should I use? What squash should I have? What should the Miller head be toqured to?

    3. Where do I start with my jetting? (low/high)

    4. Do I need water injection with the coffman pipe? or can I hard jet the pipe?

    5. What jet sizes and location should I use? (pipe)

    6.What RPM will this motor turn and stay reliable?

    7. What weight oil should I use for the counter balance?

    8.Should I cut back the top of the Rave valve? Does this add to performance or is it to check function?

    9. Should I switch over to premix with this motor? If so what mixture 32 to1, 40to1, 50 to1?

    Please keep in mind I want this motor to run safe, I dont need to push it to the edge.....


    All input is welcome.....


  2. #2
    ou812's Avatar
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  3. #3

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    Ben has answered most of these questions but since i have a similiar setup I'll run through them.

    1)Did you get a reprogrammed MPEM? (With a different curve) Either way its a good idea to check your base timing. Set it to stock at first, then you can add 1 or 2 degrees of timing depending on how close you are to the edge.

    2) You want your deck height as low as possible so run the thinnest base gasket you can find. I used a stock head cut by Mark Underwood, I ran .058 squish. Not sure on the miller. Depends on the way the head is cut.

    3)Ben's covered jetting...I run 95 lows 167.5 mains no accelerator pump 2.0 n/s stock spring.

    4) You can either run water injection or hard jet it. It takes some tuning to set it up 100%, ben could probably help you more.

    5) Ben...

    6)Reliablity, haha. I wouldnt go over 7600

    7)You can use jet pump oil, i use 90 wt gear oil.

    You mean cut the black plastic cap? You can, but all its going to do is show you if your raves are functioning, You should be able to feel them working without having to see.

    9)I'd premix 40:1

    Did you open up the stinger of the coffman pipe? You should open it up a few mm's, especially if you want to attempt to run on pump gas. I'd suggest mixing in at least 1/4 tank race 3/4 93octane.

    Just some info I've found when i built my ski a few years ago.

  4. #4
    Big bore,

    Thanks a ton for the information.

    Please keep it coming.

  5. #5
    SURFnTURF's Avatar
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    Did you open up the stinger of the coffman pipe? You should open it up a few mm's, especially if you want to attempt to run on pump gas{QUOTE}

    Dont know about opening up the stinger ?? I was under the impression from speaking to Bill O'neal and mel that reducing the stinger would reduce detonation in both a 947 set up and a 1050 BB set up. I have 2 pipes here both set up this way.
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  6. #6
    2Blue's BFF! dsolie's Avatar
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    Trevsy... I think that's the other way. Reducing the stinger produces more backpressure, more backpressure puts more load on the motor. More load can cause detonation if not tuned correctly...

  7. #7
    Quote Originally Posted by dsolie View Post
    Trevsy... I think that's the other way. Reducing the stinger produces more backpressure, more backpressure puts more load on the motor. More load can cause detonation if not tuned correctly...
    Thanks for the input guys.... As for the reduction of the stinger, do I make it smaller or lager.

    Keep the information coming... any links would be great.

    Thank you

  8. #8

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    dsolie has got it right, smaller stinger=more backpressure and heat=detonation

    you want to open the stinger up about 3mm. an unmodified coffman pipe has a 39mm stinger compared to a stock pipe which is like 50mm.

    hard to recall all this stuff, ive had many bad nights of drinking that have erased a lot of what ive learned.

    ben's post is probably the best info youre going to find all in one place.

  9. #9
    Quote Originally Posted by bigborexpl View Post
    dsolie has got it right, smaller stinger=more backpressure and heat=detonation

    you want to open the stinger up about 3mm. an unmodified coffman pipe has a 39mm stinger compared to a stock pipe which is like 50mm.

    hard to recall all this stuff, ive had many bad nights of drinking that have erased a lot of what ive learned.

    ben's post is probably the best info youre going to find all in one place.

    How do I open up the stinger?? Do you guys mean where the water goes into the pipe? or the opening that leads to the water box?


    I just spent the last few hours reading Ben 951 1050 post.. He knows his stuff.

    I hope he can chime in for me.

    Also with the 1050 motor should I run the stock pipe for Rec use, or will the Coffman pipe work well for me and not eat my pistion....

    I want to use this ski on weekends out with the guys, not in the shop working on it..

    thanks again

  10. #10
    YudLuz2's Avatar
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    If you want your motor to live on pump gas, run a oem pipe or 97 1/2
    white pipe. Don't try to run pump gas on that setup with your limited
    tunning experience on this motor setup. You will stick a motor quickly.
    Most everything you need will be in my writeup. I won't be on the board much this week. I got a couple on motors I'm trying to get built
    for next weekend. Ben

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