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  1. #1
    '03 MSX140 Hymee's Avatar
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    Aussie MSX140 Engine Rebuild

    Hi all,

    This is a continuation of my earlier thread where I was stuck getting the driveshaft out to enable engine removal.

    The update is I got the engine out with the driveshaft still in situ. It is a bit of a mission, but I got there. I'm worried about getting the engine back in, but sine I have come this far I may as well replace the 6502 bearings in the bearing carrier, along with the seals. Thanks to Greenhulk and K477 I saw some tips on the generic bearings. Same bearings as I have been using in the Supercharged RX8 project, but that is a another another story for another forum...

    I mentioned in the other thread #1 cyl was seized, lots of bits in the pot. Well, now I have the engine out and pulled it down, it was a big end bearing failure. I assume the big end failed to to an oiling problem. #2 & #3 were very well oiled, so I believe the oil pump is OK. Anyone have advice on oil pump history or problems? One shop recommends to replace it at $600, and another said they never fail, but would sell me one for $500 if I really wanted it - but thought it was a waste of time.

    Attached are some pics of various bits. It is a 2003 I bought just before Christmas @103hrs, and now @ 127hrs. It seemed in very good condition.

    First a few pics of the ski when I bought it - Just to set the scene...
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  2. #2
    '03 MSX140 Hymee's Avatar
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    Now some pics of the torn down tragedy...

    First, the complete bottom end, the lunched big end (#1), and one of other big ends - all nice and oiled.
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  3. #3
    '03 MSX140 Hymee's Avatar
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    Now the pistons...

    2 Pics of the bad one, and one of a good one.
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  4. #4
    '03 MSX140 Hymee's Avatar
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    A couples of the barrels (good) and one of the heads.

    Note the hone marks on the good barrel. Head looks OK. Even the bad one will clean up OK.
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  5. #5
    '03 MSX140 Hymee's Avatar
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    And a few of the upper crankcase.

    Note the bits of left over bearing/thrust washer in the intake port of #1.
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  6. #6
    '03 MSX140 Hymee's Avatar
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    Now for a couple of interesting questions on some observations...

    When I first tested the ski, I noticed the engine seemed to have a vibration just coming off idle, but as you reved through it, it came good. They told me it was always like that, and I trusted them and assumed it might just be a characteristic of a tripple.

    #1 - Is that sort of vibration coming off idle normal?

    I read in the manual that these engines rev to about 7200, and I also have reports that these skis can get up to about 100 km/h.

    #2 - Is there an rev-limiter? Mine revs (reved!) to 8800, even 8900 once, and I have been up to 100 to 105 km/h max. It wasn't going that hard when it poo'ed itself. Perhaps the revs are what hurt it (I would think a big YES). But why did it rev so hard?

    I thought I had a photo of the impeller to share. It is pretty nicked on the leading edge, but will probably linish up quite well. But my ski always seemed to have a bit of trouble hooking up, like cavitation I guess.

    #3 - Assuming the nicked prop is causing cavitation, could that be the reason for the over-revving, a bit like free reving an automobile engine without any load. Perhaps a "proper" impeller hooked up nicely prevents the over-rev due to load.

    Oh well, perhaps to many questions, but I'm sure you will love my pics and the story anyways. This is a pretty good place here. I've had my fair share of time on some auto forums....

    Cheers,
    Hymee.

    www.hymee.com

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Hymee View Post
    Now for a couple of interesting questions on some observations...

    When I first tested the ski, I noticed the engine seemed to have a vibration just coming off idle, but as you reved through it, it came good. They told me it was always like that, and I trusted them and assumed it might just be a characteristic of a triple.

    #1 - Is that sort of vibration coming off idle normal?

    I read in the manual that these engines rev to about 7200, and I also have reports that these skis can get up to about 100 km/h.

    #2 - Is there an rev-limiter? Mine revs (reved!) to 8800, even 8900 once, and I have been up to 100 to 105 km/h max. It wasn't going that hard when it poo'ed itself. Perhaps the revs are what hurt it (I would think a big YES). But why did it rev so hard?

    I thought I had a photo of the impeller to share. It is pretty nicked on the leading edge, but will probably finish up quite well. But my ski always seemed to have a bit of trouble hooking up, like cavitation I guess.

    #3 - Assuming the nicked prop is causing cavitation, could that be the reason for the over-revving, a bit like free reving an automobile engine without any load. Perhaps a "proper" impeller hooked up nicely prevents the over-rev due to load.

    Oh well, perhaps to many questions, but I'm sure you will love my pics and the story anyways. This is a pretty good place here. I've had my fair share of time on some auto forums...
    The Polaris 1165cc and 1192cc engines (aka 1200 and MSX 1200) do have a vibration just off idle, around 2000-2500RPM. It smooths out just above that RPM, and below.

    It is caused in part by the unbalanced pork chop shape of the crank webs.

    If you want to have a smoother engine, it is possible to rebuild the crank using 'full circle' crank webs, sourced from the Polaris twin engine cranks. Same stroke as the triple, but you would need to collect webs from two twin cranks to build a triple crank.

    Here is what my own 1165cc Polaris engine vibrates like just off idle. You can see the water below the engine develop ripples.



    All Polaris Ficht engines are rev limited by the EMM to 7200RPM. If you revved it out of the water, unloaded, I suppose you could get it to briefly rev higher, but it is hard on the engine, of course.

    In the water with the impeller loading, it should never rev that high, unless you were jumping waves and holding full throttle. Even then, 8800RPM seems awfully high.

    Normal sustained maximum RPM while riding should be just shy of 7000RPM. My own Ficht engines peak at 6800 to 6900RPM, give or take.

    For comparison, the carb'ed Polaris three cylinder red domestic engines sustain around 6700RPM while riding.

    Impeller damage can increase cavitation, and allow the engine to rev somewhat higher.

    With a properly running engine turning about 6900RPM and a good condition impeller and reasonable blade clearance to the jet pump wear ring, your MSX 140 should sustain around 100kph, or just over 60mph on smooth water.

    Hull condition, water condition, and other factors do come into play, of course.

    The dash speedo is a tad optimistic at full speed, so it may read as much as 110kph. A GPS will reveal the actual speed.
    Last edited by K447; 02-20-2010 at 01:07 PM.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Hymee View Post
    ... #1 cyl was seized, lots of bits in the pot. Well, now I have the engine out and pulled it down, it was a big end bearing failure.

    I assume the big end failed to to an oiling problem.

    #2 & #3 were very well oiled, so I believe the oil pump is OK.

    Anyone have advice on oil pump history or problems? ...
    Just to be clear, the cylinder that failed is the one closest to the front of the engine - correct?
    That would be the MAG cylinder (for Magneto, where the flywheel is located).

    Generally speaking, the oil pumps on these Polaris engines are quite robust. When there is an oiling failure, it is almost always something other than the oil pump itself. Cracked oil hoses, loose clamps, clogged oil injection ports, kinked hoses, or even a clogged inline oil filter from the tank.

    Since your 2003 model is now seven years old, I suggest replacing all the oil lines with new ones. They are a slightly unusual size, but even from Polaris they aren't that expensive.

    The oil pump is designed with a fail safe mode. If the oil pump cable to the throttle breaks, the oil arm pump swings back to a position that produces 100% oil flow, at all RPM. This protects the engine, but of course burns more oil than is normally needed.
    BTW, carefully check the oil cable for fraying just inside the ends of the sleeve.

    As long as the plastic drive between the pump and the crank snout is not damaged, the oil pump will pump oil.

    On the MSX 140 engine (and only that engine), there are four oiling lines. One hose feeds the air intake for each cylinder (just like every other Polaris triple), and an extra oil line feeds the front crank bearing, just behind the flywheel.

    This extra oil feed to the bearing is there to counter the extra heat generated by the large Ficht stator, which generates a lot more electrical power than the stator on the carb'ed engines.

    Where the oil lines feed into the throttle bodies, inside each oil nipple is a check valve. It takes a few PSI for the oil to pass through the valve. Check that the valves are not clogged, and do indeed flow oil. Perhaps the valve on your failed cylinder is clogged
    Last edited by K447; 02-19-2010 at 11:50 PM.

  9. #9
    '03 MSX140 Hymee's Avatar
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    I must have had a stupid mental moment about the RPM. I feel like a complete tosser. . Of course it was 6800 - 6900.

    Every characteristic I have described seems absolutely normal.

    I'll replace the lines as suggested. It really does now sound like a problem with the oiling to the MAG throttle body. I'd have to bet it would be that check valve being stuck. Yes - I'm aware of the 4th oil line to the crankcase - but I was unaware it only oiled the front bearing. I had assumed it also fed galleries through the crank similar to 4-stroke engines - just as redundancy.

    Thanks for all the info. Amazingly good forum, this.

    BTW - I hope you liked the photo's! I eventually got some posted for you

    Cheers,
    Hymee.

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Hymee View Post
    ...I'm aware of the 4th oil line to the crankcase - but I was unaware it only oiled the front bearing. I had assumed it also fed galleries through the crank similar to 4-stroke engines - just as redundancy.

    Thanks for all the info. Amazingly good forum, this.

    BTW - I hope you liked the photo's! I eventually got some posted for you ...
    As far as I know, all the Polaris 2-strokes (and other brands) only lubricate the crank roller bearings via oil mist, drip and splash within the crank case. No pressurized oil galleries or passages within the crank.

    Photos are always good. We can often spot things in a photo that newcomers may not notice.

    Good forum - Pay it forward, or back, when and where you can

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