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  1. #1
    Adrenaline Junkie's Avatar
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    Valve Guide Replacement

    Need to replace a valve guide and noticed the shop manual says the top of the old valve guide needs to be machined off. Is that right and why?

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  2. #2
    Eastside Powersports Slow 91's Avatar
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    To keep it from mushrooming out and ruining the cylinder head

  3. #3
    Roll Tide!! SeadooTech's Avatar
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    Quote Originally Posted by Slow 91 View Post
    To keep it from mushrooming out and ruining the cylinder head
    Slow, what if the head shop didn't machine the valve guide off..... they install all of my ATV and motorcycle guides... they r also the largest head repair shop in the area....

  4. #4
    Adrenaline Junkie's Avatar
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    I noticed the top of the guide where the seal sits is quite a bit smaller; but then it gets larger just before going into the head with a ring groove that I imagine a lip on the head seats into. Seems like it could be pushed out without mushrooming to the point the external diameter would become too large; especially since its smaller at the top. Has anyone ever replaced these without machining the top off?
    Last edited by Adrenaline Junkie; 08-04-2013 at 02:51 PM.

  5. #5
    Roll Tide!! SeadooTech's Avatar
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    I pushed some out without machining and they came right out
    Then let the machine shop install.... slow91, do u use factory or SBT guides? The SBT guides had to be termed quite a bit...

  6. #6
    Eastside Powersports Slow 91's Avatar
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    the reason you machine the guide down is because 99% of machine shops use a guide driver which fits inside the guide and you use a hammer to knock the guide out. Doing it that way will mushroom the top of the guide, so when the guide gets down to the head casting it is now larger than the guide bore and it WILL gull up the bore and your new guides will not have a press fit. I do not use anything from SBT. I usually make my own guides.

  7. #7
    C Doo's Avatar
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    Does anyone know the valve heights for these rotax engines?

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    Quote Originally Posted by Slow 91 View Post
    the reason you machine the guide down is because 99% of machine shops use a guide driver which fits inside the guide and you use a hammer to knock the guide out. Doing it that way will mushroom the top of the guide, so when the guide gets down to the head casting it is now larger than the guide bore and it WILL gull up the bore and your new guides will not have a press fit. I do not use anything from SBT. I usually make my own guides.
    The absolute GOD of 4-tech engine building/machining has spoken.
    Nothing more needs to be said.

  9. #9
    C Doo's Avatar
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    why is there no mention of height in the manual for valve replacement?? Should we not have some figures/tolerances??

  10. #10
    Adrenaline Junkie's Avatar
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    Quote Originally Posted by C Doo View Post
    why is there no mention of height in the manual for valve replacement?? Should we not have some figures/tolerances??
    From the pictures I've seen it looks like the Valve guide pusher (p/n 529 036 087) makes contact with the head and prevents you from pushing it too far in. Maybe someone who has one of these can verify that.

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