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  1. #1
    Top banana's Avatar
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    Compression readings

    Just checked mine 1=125 psi 2=120 psi 3=130 psi can anyone tell me if this good can not find readings in the manaul.


  2. #2

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    123

    What do the 1,2, and 3 stand for? Is it the Stage you're referring to?

  3. #3
    Red Devil's Avatar
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    He is referring to cylinders 1, 2, and 3....Banana, I am assuming you did this while the engine was warm and not cold???? If it was cold, ya gotta check it when the engine is warmed up. Your readings look like a cold check...

  4. #4

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    Got it. The compression usually depends on what set up you're running?

  5. #5
    Red Devil's Avatar
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    Quote Originally Posted by smc
    Got it. The compression usually depends on what set up you're running?
    Yep, Right now all 3 of mine read at 123. When it was stock, they read at 135....

  6. #6

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    Poundage

    Red,
    Do you have heavier injectors?

  7. #7
    Red Devil's Avatar
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    Quote Originally Posted by smc
    Red,
    Do you have heavier injectors?
    Yes, the 55's.......

  8. #8

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    My Boat

    My boat runs 42's and Rotax in Austria issued compression to 135 for optimal performance. Why would yours be so much lower or mine so much higher?

  9. #9
    excess's Avatar
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    Quote Originally Posted by smc
    My boat runs 42's and Rotax in Austria issued compression to 135 for optimal performance. Why would yours be so much lower or mine so much higher?
    he most likely has lower compression pistons.

    Compression is like saying the life of the cylinder and the pressure it builds inside where the piston is. Over time its normal for the motor to start giving up a little and compression drops and should be pretty even across all cylinders unless you have a problem. Compression doesnt have a standard like "135", every machine or setup can vary and still run hard or be at its ideal level. Some people like low compression because it is safer to run more boost others like high compression because of how snappy the engine gets but again this is in general not talking about the RXPs, we really dont have the flexibility like a motorcycle where they make tons of different size base or head gaskets that affect a motors compression. Also tuning completely changes with compression it can go eather richer or leaner and its much harder to adjust on these skis unless you have something like an EMS and still it not as easy as a carb and jets. Its all about combination and ultimately what you want to build the ski for, quickness, top speed reliability, full blown race, etc.

  10. #10

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    Austria

    Thank you for that explaination. With this set up (Mark's former boat,) and combo of his mods and engine blueprinting as soon as the compression was raised the boat became both faster and quicker. It also burned less gas.

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