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Thread: Tri-z Carb

  1. #1
    Join Date
    May 2008
    Location
    Tenn
    --
    542

    Tri-z Carb

    Just curious and maybe it has been addressed already.
    I noticed the 1980's YZ250 had a 38mm carb but the 85 Tri-z had a 32.
    Any idea why such a difference?
    Thanks
    Just-Tri-It

    :Trikes Owned:
    1985 Tri-z's 3
    1986 Tri-z
    1984 YTM 200ERN 1

  2. #2
    Join Date
    Mar 2010
    Location
    Arizona
    --
    782
    I think there are a number of reasons. One, they are different cylinders with different manifolds, port specs, etc. Two, a smaller carburetor gives you more bottom end. A three-wheeler has more weight and will be ridden more often on slow trails, so Yamaha thought it would be better for it's intended use. Plus, by 1980 manufactures had already been at war for more than a decade building motocross bikes, so their design philosophy was less conservative. Who knows, if 3-wheelers had been around a few more years they may have ended up with 38mm carbs off the floor.

  3. #3
    3Z with Fangs! is offline At The Back Of The Pack Arm chair racerFirst time rider
    Join Date
    May 2018
    Location
    Virginia
    --
    184
    Two things, YZ250=Race bike Tri-Z 250 trail machine. Even still the Tri-Z is pretty "detuned" from the factory and a few mods really bring it to life. With that said there's a 39mm PWK on mine with mods to the cylinder, milled head, good pipe etc. It takes a little but it can come to life.

  4. #4
    Join Date
    May 2008
    Location
    Tenn
    --
    542
    Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
    Thanks
    Just-Tri-It

    :Trikes Owned:
    1985 Tri-z's 3
    1986 Tri-z
    1984 YTM 200ERN 1

  5. #5
    Join Date
    Mar 2010
    Location
    Slidell, LA
    --
    4,528
    Quote Originally Posted by Just-Tri-It View Post
    Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
    Thanks
    Drill an 1/8” diameter hole in the return line T fitting.
    Feedback for yaegerb: Click Here

    Need something blasted or polished or both? Send me a PM

  6. #6
    Join Date
    Mar 2013
    Location
    Baldwin, Wi
    --
    598
    Quote Originally Posted by Just-Tri-It View Post
    Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
    Thanks
    He's got a 39mm it probably came off a sled with the smaller float needle and seat. Designed to be used with a fuel pump.
    85 Tri-z Power valve on Inverts
    85 Tri-z Basket Case
    01 gsxr750 engine/Tri-z frame (long long way from complete)

  7. #7
    3Z with Fangs! is offline At The Back Of The Pack Arm chair racerFirst time rider
    Join Date
    May 2018
    Location
    Virginia
    --
    184
    Quote Originally Posted by Just-Tri-It View Post
    Do you have issues with the 38 flooding because of the fuel pump pressure that some have talked about? If so, how did you correct it?
    Thanks
    If you were asking me, no, I have a 39mm Sled carb. No issues at all.

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