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Thread: RPMS

  1. #1
    smitty
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    RPMS

    New rider here.
    I have an MSX140 and frankly some of this stuff I'm reading on here scares the hell out of me. It's running good right now but I'd like to know what is the max RPM's I should be looking for.
    To tell you the truth I ran some regular 2cycle oil thru it and I think it lost some performance. Slow out of the hole etc. I went back to top of the line synthetic today and it ran alot better and smoother. I could only get about 5700 RPM's at WOT and close to 53MPH. Is that normal. I'm so new at this I have no baseline to compare it to.
    Any info/advice would be appreciated.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    My 1200 Ficht engines (MSX 140 and Virage TXi) turn about 6900 RPM, give or take, at WOT on smooth water, and around 60mph measured with a GPS.

    The MSX speedometer reads a little higher than you are actually doing, so you should see speedometer numbers in the low-mid 60 range at WOT.

    5700 RPM is definitely low, and you should investigate.

    Have you downloaded the Service Manual?

    Checked compression?

    Make sure you are using the correct NGK PZFR6H spark plugs - no substitutions.

    What do you mean by 'regular' 2 stroke oil? What oil did you use?

    Did the max RPM change from earlier?
    By how much?

  3. #3
    smitty
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    RPMS

    K447

    Thanks for the quick reply. Yes I have down loaded the service manual and when I say regular 2 cycle oil I mean 2cycle outboard oil.
    I have not riden this thing much so I really cant tell you max RPMs I've gotten.
    There,s a real long story behind this thing but I keep it short. I bought this thing a couple years ago from a guy I was, lets just say, aware of. I trusted the guy and didn't test drive. Well the first time to the lake started it up ran for about 5 mins. and quit. Messed with it some, finally took it to repair shop. They new the boat, just worked on it to the tune of $800.
    They looked at it did compression test, front cyld shot! $1500 later out of my pocket they fixed it.
    Our lakes have been so low down here the boat has sat for a year, finally started riding it this year, now sorry for the long rambling but that's my story.

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Well, lets start with the basics.

    How many engine hours does the MFI display show?

    What is the compression in each cylinder?

    Correct PZFR6H spark plugs?

    2-stroke oil, Polaris calls for TC-W3 type oil.
    Is that what was used?
    What do you have in there now?

    Do you know what other repairs were done before the MAG cylinder was repaired?

    What did the shop do for your $1,500?

    Is the service shop an authorized Polaris PWC dealer?

    Do you know if this machine has EVER run 100% right?

  5. #5
    ph2ocraft's Avatar
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    Check fuel pressure and crank index, work on the little things afterwards.

  6. #6
    smitty
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    RPMs

    Lets see,
    Yes the shop is a certified Polaris repair shop. They bored and sleeved all the cylds. Installed new pistons, rings, wrist pins and bearings.
    No I dont know if it has ever turned over 6500 RPMs. Fastest I've ever gotten out of it is 55.
    I'm running the highest grade sythetic in it that my local shop sells. I'll check to see if it's TC-W3. If it's not I'll find some. I've got the right plugs in it.

    I was out today and got 6200 RPMS. It seems to get better everytime I ride it.
    I've read on here about the throttle position sensor going bad. Could that have something to do with it??

    I appreciate the advise!

  7. #7
    smitty
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    Forgot, its only got 61 hours on it.

  8. #8
    Quote Originally Posted by smit1r1rich View Post
    Lets see,
    Yes the shop is a certified Polaris repair shop. They bored and sleeved all the cylds. Installed new pistons, rings, wrist pins and bearings.
    No I dont know if it has ever turned over 6500 RPMs. Fastest I've ever gotten out of it is 55.
    I'm running the highest grade sythetic in it that my local shop sells. I'll check to see if it's TC-W3. If it's not I'll find some. I've got the right plugs in it.

    I was out today and got 6200 RPMS. It seems to get better everytime I ride it.
    I've read on here about the throttle position sensor going bad. Could that have something to do with it??

    I appreciate the advise!

    Why did they SLEEVE the cylinders??? They were nikasil lined before and if they installed cast iron sleeves and did not redo the porting then you may never get the rpms back

    If they did this work for you make them put the machine on digital wrench and find out why it wont rpm
    Something smells fishy here to me

  9. #9
    smitty
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    K447,
    I started messing with the throttle cable while riding the ski today. With the trigger wide open you can put pressure on the throttle cable and the rpms and speed jump up. I was unsure how much pressure to put on it with my finger but I got 6500 rpms and about 60mph out of it.
    I think this problem may be fixed by adjusting the thottle linkage correct? If so, I believe I can do this myself. Please let me know if I'm correct and if there's any tricks or f#$k ups I need to watch out for. I will go over the manual before attempting.
    Thanks in advance

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Arrow Adjusting throttle cable for correct freeplay at thumb lever

    Quote Originally Posted by smit1r1rich View Post
    ...With the trigger wide open you can put pressure on the throttle cable and the rpms and speed jump up. I was unsure how much pressure to put on it with my finger but I got 6500 rpms and about 60mph out of it.
    I think this problem may be fixed by adjusting the throttle linkage correct? ...
    You want to adjust the throttle cable so there is just a tiny bit of slack (0.020 - 0.060" measured at the thumb lever) in the cable when there is zero pressure on the thumb lever. See page 35 in the MSX 140 Service Manual.

    Be sure you are adjusting the throttle cable, not the cable to the oil pump. You loosen the locking nut on the sleeve of the cable at the throttle body, and then turn the adjustment until the slack is taken out of the thumb lever.

    Do this in stages, and operate the thumb throttle to exercise the cable. As you get close, snug the lock nut, and check that the throttle body does indeed return to idle position. Take the flame arrestor cover off, so you can watch the throttle plates open and close.

    When you have it right, the throttle plates will be closed at idle, and start moving almost immediately when you move the thumb lever. When you squeeze the thumb lever all the way, the throttle plates should open to wide open, or close to that. The last few degrees of opening are not super critical.

    After you have finished adjusting, while watching the throttle plates, swing the steering full left and right. The throttle plates should not move when the steering is operated.

    Once that is done, you might want to check that the oil pump cable is properly adjusted (page 34 in the Manual). Some of us adjust the oil pump cable so that the index mark is a line's width more towards 'open throttle' at idle than the spec. This provides a bit more oil at low RPM, to increase engine lubrication. A small mirror helps a lot with this adjustment, down on the front of the engine.

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