Few questions from a newb!
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Thread: Few questions from a newb!

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    Junior Member JCope79's Avatar
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    Few questions from a newb!

    So last year I purchased a 86 TRX. Now I’m in the process of rebuilding the motor. After some research I’ve realized I have a 86 ATC bottom end and a 85 top end with no port and a 87 or later crank. Also before I blew it up it had a 87-89 piston with no spacer plate. I never could get it dialed in. This time around I plan on running a 85/86 piston with a spacer plate and will have the cylinder ported and polished. Is this a safe setup for woods riding or would a short rod crank with no spacer plate be better? Help me out!!

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    Junior Member scrappy's Avatar
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    That will make a great combination with the right intake & exhaust system.

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    Senior Member american opel's Avatar
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    imo i wouldnt port a 85 cylinder.i would do a 87-88.and if your cylinder is under 68mm no reason to run a 85-86 piston and spacerplate.

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    Junior Member JCope79's Avatar
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    I have a 38mm air stryker and vforce3 reed cage on intake and PT trx89race. It’s what I have without spending a whole lot of money.

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    Member The Norm's Avatar
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    Quote Originally Posted by american opel View Post
    imo i wouldnt port a 85 cylinder.i would do a 87-88.and if your cylinder is under 68mm no reason to run a 85-86 piston and spacerplate.
    Could you provide some supporting information about your statement? The op's proposed engine set up is pretty much exactly what my son has powering his R and it flat out rips. He humbled a raptor 700 and a yfz in a 300 foot drag this summer.
    I had a bdt engine once....It sucked!
    Current: Hybrid Engineering 391R
    Future: Some other awesome engine built by Hybrid Engineering!

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    Member The Norm's Avatar
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    I would check out your ignition system before you fire up the newly rebuilt engine just to be sure. If you can't get it dialed in jetting wise it could be a contributing factor. Also a leak down test can save you a ton of money and frustration....
    scrappy likes this.
    I had a bdt engine once....It sucked!
    Current: Hybrid Engineering 391R
    Future: Some other awesome engine built by Hybrid Engineering!

  8. #7
    Junior Member scrappy's Avatar
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    Go ahead & run that long rod crank with an 85-86 style piston & spacer plate. I ran that combo in my 86trx for over 20 years & never had any issues. You can also have that 85atc cylinder ported & set up for woods riding & you will probably love it. OEM cylinders can be made to run very well & there reliable.

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    Senior Member american opel's Avatar
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    Quote Originally Posted by The Norm View Post
    Could you provide some supporting information about your statement? The op's proposed engine set up is pretty much exactly what my son has powering his R and it flat out rips. He humbled a raptor 700 and a yfz in a 300 foot drag this summer.
    what do you need to know.the 85 cylinder has the worse factory port and without the intake support like the 86+ i wouldn't spend the money to port it.some like the sr piston as for cylinders the intake support on the 87-88 and port is also better.so not sure what your question is.ask and i can try to answer.
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  10. #9
    Member The Norm's Avatar
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    If you have a top notch 250R engine builder like Pete at Hybrid Engineering set up your cylinder you will have nothing to worry about. Pete can take your cylinder and make it do everything you want it to. Like I said before my son's R has pretty much the same engine set up as you are going with. It is a very respectable engine.
    scrappy likes this.
    I had a bdt engine once....It sucked!
    Current: Hybrid Engineering 391R
    Future: Some other awesome engine built by Hybrid Engineering!

  11. #10
    Junior Member JCope79's Avatar
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    I’m actually fortunate enough to have a father who is willing to provide his expertise for free. He ports! I polish!

    As far as air leaks...i had a faulty crank seal that proved to be the culprit for this rebuild.
    scrappy likes this.


 
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