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  1. #1

    Join Date
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    95 slt 750 please help

    hey guys i have a situation i need help with.. a few months ago the ski ran like crap so i checked compression and the pto cylinder was gone 40 psi so i pulled head and the piston had a hole in it dead center the size of a nickel i replaced it with a new piston and rings.. i installed new gaskets and bolted it back up.. when i tried to start it it would fire so i pored some fuel down the carbs and tried again and again it.. nothing i pulled plugs to check for spark and it has spark when i put the plugs back in and hit the button BBAAAAMMMMM BACK FIRE so loud my wife tinkled alittle lol so after doing that a few times i decide to pull the pto plug and check compression again holy crap 40 psi still so i pull the head and it is in great shape nice and tight.. i put the head back on torque it down and try to start it with the plug out in the pto cylinder and it starts up everytime but as soon as i put the plug in it will not start only back fire every once in awhile..


    what the heck could it be

    a hole in the case or a bad crank seal ????

    why no compression???


    please help guys...


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    A hole in a piston is typically caused by too lean fuel delivery into that cylinder. Normally that is caused by a clogged carburetor, or other weakness in the fuel system.

    Other than replacing the damaged PTO piston, did you take the carb(s) apart and clean them internally?

    If you still have low compression after replacing the damaged piston, there is something wrong in that cylinder. Did you check for damage or slop in the connecting rod on the damaged cylinder?

    Also check the crank index.

    Polaris Fuji (blue) engine

  3. #3

    Join Date
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    no i sure didnt check any slop or the carb

    and i guess the cylinder might be bad...

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Are there any scratches in the cylinder walls?

    Also make sure the head gasket is good.


    What is the piston clearance, and ring gap?

    Either of those can give low compression readings.

  5. #5
    bowsniper's Avatar
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    Remember, just because you changed a piston, doesn't necessarily mean that fixed the problem. That hole was BECAUSE something else is wrong. thats just the result. You must find out why that happened. Then fix the compression problem..
    Guys on here suggest a triple carb update along with gas cap updates and fuel line swaps and other goodies to check. Read some of the posts in the how-to section.!!! read read read, you'll learn lots about your ski!
    Otherwise follow xlint89's advice and k-447. they know thier stuff.
    A leakdown test would tell you a lot. check the other cylinders too . Take out all plugs, full throttle open while cranking. 5 good cranks per cylinder. then repeat again to be sure. then go from there.


    Possible crank index problem with the backfiring? Did ya flip it? or swamp it? hmmm..

  6. #6

    Join Date
    Aug 2009
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    Did you take a look at the reeds and also I bought a 750 last year that had a piston get a hole blew in it and all the guy did was put a piston back in it. When I got it started it only ran about 15 min in the water before it took the cranke out of it. So I would recomend taking the motor out and checking for metal in the bottom end.

  7. #7

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    Thanks guys i will do more ckecks

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