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  1. #1

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    low compression in the PTO cylinder

    i have a 1996 SLT 780, the pto has just under 120psi ( like 118 ) and the other two are about 145psi can i run it like this? does it just need rings in that cylinder?


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk.

    Unfortunately the PTO cylinder compresson is very important. It drives the fuel pump, which fuels the carbs, so it's a must for good compression. A strong "signal" moves the fuel pump diaphragms much better than a weak one. A weak "signal" will not move the diaphragms as well, thus resulting in lower fuel pressure. Low fuel pressure can lead to a lean (lack of fuel) condition, and cause piston damage at high RPM.

    I'd suggest you remove the cylinder head and see if there's any visable signs of damage or wear.

    You normally want the maximum of 10% difference between the cylinders as far as compresssion numbers goes.

  3. #3

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    is it ok to just replace the rings if there is no other damage? and what are the chances that this is all i need?

  4. #4

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    i was reading up on compression testing and noticed that they recommend to hold the throttle open. i did not do this, will this change the results that much?

  5. #5
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    Quote Originally Posted by lippyat13 View Post
    i was reading up on compression testing and noticed that they recommend to hold the throttle open. i did not do this, will this change the results that much?
    Try the test again and report back.....

  6. #6

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    its like 20* out there and the ski is under some snow it may have to wait till the snow melts

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Normally it's not just worn rings....

    Often it's damaged piston and/or scuffed cylinder.

    Throttle should be help open when compression testing, but if all were done without it, and only 1 was off, I wouldn't think that would be the problem.

    You can retry the compression test, but if it's low, then remove the head for a better look at what's going on.

    Is this a ski you just bought?

  8. #8

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    Quote Originally Posted by xlint89 View Post

    Is this a ski you just bought?
    yes i picked up 2 with a trailer. the 95 slt75 had perfict compression all were exactly the same at 120. the trailer is in perfict condition and he also had covers and jackets all for $1700. i think i did good.

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    You did xlint!!!

    Well, pull the heads. There's a chance the previous owner may have just swapped out 2 new pistons and left the PTO....

  10. #10

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    i got them from the 2nd owner who had them from 2002. he told me he never did any work on the motors.
    is it possible to reuse the head gasket or should always replace it when I remove a head?

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