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Thread: How to power valve your Tri-Z

  1. #1
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    How to power valve your Tri-Z

    Well, I thought i'll go ahead and start this thread for anyone that's curious.

    I've started my engine assembly and i've been documenting it.

    In case anyone wonders why you would do this, it has been said that this drastically improves overall performance of your engine, giving it more torque thru-out the powerband.

    First your going to need to locate a complete 83-87 YZ250 engine. You can either use the whole YZ engine or just the components related to the power valve, which is what I did. It works the same either way.

    The first part neccessary to swap is the crank gear, if you choose to use the Tri-Z lower engine. The gear off the YZ is a double gear used to operate the power valve governer.

    Next you need to install a bearing in the Tri-Z case for the governer. These are still available from Yamaha for $11.00
    Attached Thumbnails Attached Thumbnails Powervalve 1.jpg   Powervalve 2.jpg   PowerValve 3.jpg  
    2007 YAMAHA YTZ450 went to a great home RIP Sam


  2. #2
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    Here's a couple shots of the YZ and Tri-Z cylinders beside each other. Notice the volume difference in the intake.

    The intake is also angled slightly to the left, which is an issue we will deal with later.
    Attached Thumbnails Attached Thumbnails Powervalve 4.jpg   Powervalve 5.jpg   Powervalve 6.jpg  
    2007 YAMAHA YTZ450 went to a great home RIP Sam


  3. #3
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    Now we'll address the modifications neccessary to adapt the Tri-Z clutch cover for the power valve governer.

    First a bearing needs to be installed in the clutch cover to support the governer. These are still available from Yamaha for $11.

    Then you must knock out a punch plug from the Tri-Z cover. All of the casting and machining to accept the power valve equipment is done from the factory. You need to simply install it.

    Once the plug is out you'll need a seal to replace it. This is still available from Yamaha for $6.00. Then just install the rod assembly and governer from the YZ engine and cover into the Tri-Z cover.
    Attached Thumbnails Attached Thumbnails Powervalve 7.jpg   Powervalve 9.jpg   Powervalve 8.jpg  
    2007 YAMAHA YTZ450 went to a great home RIP Sam


  4. #4
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    This thread has been done before. Can't wait too see the finished product!!! Wish i had one.
    1985 YAMAHA TRI-Z 250 sold

    2006 YFZ 450

  5. #5
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    That's where i'm at so far. I'll install the cylinder and finish it up later this week. Still waiting on the piston. I'll also cover how the install goes into the bike.
    2007 YAMAHA YTZ450 went to a great home RIP Sam


  6. #6
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    Very informative Derrick! Great thread!

  7. #7
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    I do not suppose you have a printable form of instruction sheet.

    85 Tri-Z's
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  8. #8
    Join Date
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    Looks much easier to adapt the YZ cylinder & governor to the Tri-Z, than it was to adapt the CR cylinder & governor to my ATC 250R. Now every Tri-Z's gonna be powervalved! Cool thread Derrick!
    Red Rider's Sand Machine Updated 07/23/14

  9. #9
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    Which way does the stock YZ kicker go? Front or rear?

    85 Tri-Z's
    85 Quad-Z,
    85 YT175 For sale,
    83 YTM 225DX,
    83 YTM 200L For sale,
    82 Tri-Zinger 60 For sale,
    8? YTZ 80 Conversion,
    85 YT 125,
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    05 YFZ 450,
    99 V-Star,

  10. #10
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    Kicks rear. When I do my other YZ engine, I'm going to do it the opposite way and use the YZ bottom end. So, i'll be switching the kicker gears. It will be a couple weeks before I get to that though. I'll add all that info to this thread as well.
    2007 YAMAHA YTZ450 went to a great home RIP Sam


  11. #11
    Join Date
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    So it is not neccassary to use the whole Tri Z side cover on a YZ bottom end?

    85 Tri-Z's
    85 Quad-Z,
    85 YT175 For sale,
    83 YTM 225DX,
    83 YTM 200L For sale,
    82 Tri-Zinger 60 For sale,
    8? YTZ 80 Conversion,
    85 YT 125,
    89 Pro Hauler 230,
    05 YFZ 450,
    99 V-Star,

  12. #12
    Join Date
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    the easiest thing to do ,like i did, was swap the whole top/ bottom in place, my intake is straight in, yours it at an angle..mmmm....great information for the ones with questions with this swap, next i think im going for the 426 or 450 thumper in one , problem is those engines cost way too much
    Attached Thumbnails Attached Thumbnails billet intake.jpg   motor is in.jpg  
    1985 With "86" Plastic's,Custom 12" Alluminum Extended Swing Arm,39MM PWK,"TRX" Filter,9 Paddle TALLER HALLER'S on 11" Wide Rim's,LOT'S of Stainless,LOT'S of Alluminum,LOT'S of PowderCoating,NOTHING Stock..

    FASTEST Tri-Z on The Planet...MAKE A NOTE !! and the SECOND FASTEST, WRITE IT DOWN AGAIN!!!

  13. #13
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    What year motor you got Derrick? Mine is an 87 and its slanted to. I know 88 on up went back to 6 pedal reeds, and had a straight intake.

  14. #14
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    Both of mine are 87's.
    2007 YAMAHA YTZ450 went to a great home RIP Sam


  15. #15
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    Good stuff Derrick! Now hurry and finish it!
    1986 Tecate
    1984 Tecate
    1985 Tri-Z
    1986 ATC350X
    1985 ATC250R (2)
    1985 ATC125M (2)
    1982 ATC70 - Original Owner

    175 TriMoto Frame with Pro-Tec Rear Suspension

    3-Wheelin' since '82

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