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  1. #1

    MSX 140 rear cylinder missing

    I just bought a 03 Polaris MSX 140 and it seemed to run okay on the trailer when I bought it but I put in the water and it's definitely down on power and sluggish. I have good spark, I have 125 compression in all cylinders and I have 25 psi of fuel pressure. The rear plug I can see is gas fouled but I can swap plugs with another cylinder and the fouled plug will clean up and the rear cylinder will gas foul the other plug. The previous owner must have taken the air filter out because there isn't one in there now and I'm wondering if it might have ingested something and broke a reed valve. I know I have a good strong spark on all cylinders and 125 compression on all cylinders should definitely be enough to fire the cylinder the only thing I don't know how to check is the fuel injection system is there any way short of taking it to a dealer that I could get to the bottom of this problem.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Are the correct spark plugs installed? Must be NGK PZFR6H.

    The ignition system on the Ficht engines is quite powerful so the spark should normally be very strong. However, the Ficht ignition is also unusual and does not tolerate incorrect ohms or wrong parts. It is a multi-strike ignition, per power stroke.

    Ohm check the spark plug wires. You can also swap adjacent ignition coil primary and secondary together to see if the problem moves.

    Also check that each ignition coil wire is indeed connected to the correct cylinder. I have posted the fuel injector and ignition coil primary wire colors for Ficht engines previously. Additional info can be found via my signature link.

    If you suspect the intake reeds, best method is to visually inspect them. Not too hard to remove the throttle body rack and intake manifold. Be sure to make notes and take digital photos before you start and as you work. Pay attention to how the oil pump cable is routed and adjusted.

    When you put it back together be sure to adjust the throttle cable for correct slack.

  3. #3
    It does have the correct NGK spark plugs. The plug wires all ohm out okay. The reason why I suspect read valves is that I have oil on and around the throttle body butterfly on the rear cylinder but it could just be because it's not firing correctly. I have a filter element ordered and on its way but I wouldn't think that would've caused a problem because a PWC is operated in a somewhat clean environment.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by LM53 View Post
    It does have the correct NGK spark plugs. The plug wires all ohm out okay. The reason why I suspect read valves is that I have oil on and around the throttle body butterfly on the rear cylinder but it could just be because it's not firing correctly.

    I have a filter element ordered and on its way but I wouldn't think that would've caused a problem because a PWC is operated in a somewhat clean environment.
    The mesh screen in the air intake is not an air filter. It is a flame arrestor, designed to prevent engine backfires from igniting gasoline fumes that may be present inside the enclosed hull.

    With the flame arrestor cover removed and the engine running, look for a mist cloud above the rear cylinder air intake. A broken reed valve will pulse oil+air mixture up and down the throat, which can sometimes be seen as a cloud or droplets. The teltale is if it only appears above the rear throttle body intake.
    Last edited by K447; 04-29-2015 at 06:43 PM.

  5. #5
    Actually I know it's a flame arrestor and not a filter but in the Polaris parts microfiche they call it out as an air filter.

  6. #6
    Thanks for all your help K447. I decided to hook some water up to it and run it with the spark arrester off and I could feel suction in the two front cylinders and I could actually feel a blowback out of the rear cylinder. So after pulling the throttle bodies and the intake here's what I found.
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  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by LM53 View Post
    Thanks for all your help K447. I decided to hook some water up to it and run it with the spark arrester off and I could feel suction in the two front cylinders and I could actually feel a blowback out of the rear cylinder. So after pulling the throttle bodies and the intake here's what I found.
    It should run better with a good set of reeds in there

    Inspect all the reeds carefully while you have it apart.

    Hell, inspect everything you can get an eyeball, mirror or smartphone camera on.

    If you seal some duct tape over the engine intakes you can even swab under the motor and clean it up down there. Might even find lost tools and spare parts

  9. #9
    if I had to guess I would say this PWC operated without a spark arrestor probably ingested something that broke that Reed. that's just my guess

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by LM53 View Post
    if I had to guess I would say this PWC operated without a spark arrestor probably ingested something that broke that Reed. that's just my guess
    That reminds me, some of the flame arrestor covers have an aluminum spacer/sleeve under each bolt. When lifting the cover off after removing the bolts sometimes the sleve(s) would drop out of the cover and could fall into the throttle body throat. If one did not notice that the spacer had fallen, it might end up going into the engine.

    At the moment I do not recall if the flame arrestor cover on the MSX 140 had the problem with the loose cover bolt spacers.

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