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  1. #1

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    Compression in an MSX 150

    Hello. I'm going to look at a MSX 150, that runs good, hard starting when warm. The seller states low compression, 120-120-120. Is this a terrible number, or low, but ok. Just checking, as the price is right. Thanks,

    Bill


  2. #2
    Moderator HiPeRcO's Avatar
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    150 has only two cylinders, are you sure its not a 140? If its a 150, then 120psi is low, likely either cylinder wall plating failure and/or head gasket. Be prepared for a major project if you decide to buy it, and don't pay a lot for it. The good news is that the tech support here at the Hulk is incredible, the guru's are walking me through my recent 150 purchase that just might be a keeper

  3. #3

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    It is a 150. I miss spoke. I'm going to get it now. $800 with trailer!

  4. #4
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    Be careful. If you get a 150 and the engine needs work, prepare for a lot of headaches and be prepared to spend a lot of money. Those are not cheap to fix at all.

  5. #5
    ripcuda's Avatar
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    Even at $800 with a trailer... if you have Nikasil failure... and 120psi is probably due to that (thus hard starting in the water). You will have to remove the engine and completely rebuild it to fix the cylinders. You'll either need to sleeve the block or have the cylinders replated. You are looking at least $2k in parts and service alone. With you doing all the wrenching, engine removal, engine disassembly, engine prep, engine rebuild, engine reinstall.

    You up for all that? Consider carefully.

    Cheers!

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  7. #6

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    Thanks for the advice. Will running it at 120 psi cause damage to the motor?

  8. #7
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    At 120 psi the motor may already be damaged. Unless you are prepared to spend a few thousand dollars on repairs you should probably pass on this.

  9. #8
    ripcuda's Avatar
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    With 120psi compression... the ski will be very hard to start in the water. You'll need to lift the left rear corner out of the water (exhaust port) to alleviate exhaust back pressure while starting.

    And if you do have Nikasil plating failure (common)... you'd only be making it worse.

    120psi is not healthy. Plan for a full rebuild.

    Cheers!

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  11. #9

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    Did some magic, and got the compression back up to 135 each cylinder. Brought it out to the water, trailer test run, to see how it would run. started right up. Smoked a little at first, as expected from my magic trick. ran it at idle for 15 mins on trailer, with no problems. Every few mins, I would increase rpms up to around 2500, and hold for a few sec to see if it would fluctuate. Stayed steady. I got brave, and took it for a ride. I have never drove an MSX or a 4 stroke. The water was choppy. This thing is quiet. Good throttle response. It is slower out of the hole than my Virage Txi, but faster on the top end. The ride is awesome on rough water. I would have been beat to death on the Virage today. I tried multiple times stopping it, sitting for a little bit, then starting it. No problem starting at all. If it doesn't rain tomorrow, I will take it out for a little longer ride. Very happy with the MSX platform. Can't wait to get the MSX 140 up and running!

    I forgot to bring my GPS. The lie-o-meter said 65mph. I'm guessing I was doing somewhere in the low to middle 50's.

    Edit: It idled at 1550 rpm. No fluctuation. What should this idle at?
    Last edited by Bigbill55; 05-16-2015 at 09:57 PM.

  12. #10

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    After I give it a bath, and get it nice and shiny, I will post some pics. Black plastics, and hull. Silver top side.

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