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  1. #1
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    MSX 140 low compression & piston replacement question

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    Last edited by chc3; 01-12-2015 at 10:25 PM.


  2. #2
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    How is it running? If its developing full power and normal max RPM I wouldnt worry about it.

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    Last edited by chc3; 01-12-2015 at 10:24 PM.

  4. #4
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    Some compression testers read low.
    My $45 tester will read 125 psi while my buddies craftsman top of the line tester will read 150psi.
    If they are even and the ski runs fine what's your worry???

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by chc3 View Post
    lost top end running 6600 rpm wot and it hesitate till it gets to 4500 rpm
    What do you mean by that?

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    6600 isnt bad. Thats about all mine runs.

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    Last edited by chc3; 01-12-2015 at 10:24 PM.

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    Click avatar for tech links/info, donation request K447's Avatar
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    What condition are the cylinder walls in? If they need replating then that should be done properly.

    You say you like 150 PSI ... Do you have experience tuning these Ficht engines?

    Hesitation may not be related to compression. The first thing I would change would be the TPS. Check all the external sensors that feed the EMM and monitor the injector voltage while riding.

    Where are you located? What air temperatures?

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    Last edited by chc3; 01-12-2015 at 10:24 PM.

  10. #10
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    Yes you need them. There are warnings all over the place in the Polaris manual about making sure you have them in place. I would tend to think machining the heads on a FICHT engine is a really bad idea. These are already running ragged lean, adding more compression to the equation would cause more heat and possibly detonation issues. If you want to mod an engine stick with carbs. If you want simple gas and go simplicity, the DI is the way to go.

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