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  1. #1

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    MSX 150 - Dropped Intake Valve - Any Thoughts?

    Here is a shot of the head off my MSX 150 with 44 hours on it. Garage kept, proper maintenance, etc. The picture has been seen by more than a few knowledgeable mechanics and I still don't have a decent explanation why. Any thoughts would be appreciated. Engine was turning about 6k when it went.
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    The exhaust valves do not match and the head was never taken apart prior to this (plenty of powder coat on everything).


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    What does the other head look like?

    Any signs of rust on the valve stems?

  3. #3
    PolarisNut's Avatar
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    Valve spring ok? More than likely, some rust got on the valve guide/stem and the valve "hung up" and the piston smacked it. Happens on some of the the Sea Doo 4tec motors.

  4. #4

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    The rest of the head looks good. Springs, retainers, shims were all in place. Not sure about the rust. It had 8 hours of use on it in the "new" season and it was running the day before this happened.

  5. #5
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    sometimes valves will just do that.a lot of the seadoo guys will run there motors beyond the intinded rpm range or run stiffer springs and pull the stock valves apart like that.if you plan to rebuild the motor check into desperados reflash for the msx 150's,might save you a premature rebuild down the road.

  6. #6

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    Nearly Rebuilt

    Not wanting to give up on my MSX 150 (although I probably should have as I am not an expert and only have a one-car garage and basic hand tools), I decided to rebuild it and now that the engine is nearly assembled I thought I would share a few observations and give thanks to all that helped bring this project together.

    First a little background. As you can see from the head picture above, the engine suffered a major hit with not even 45 hours on it. Sadly, the plating was in perfect shape. Before that broken intake valve head lodged itself into the cylinder head it bounced around the cylinder and took out the piston/pin/rod and a decent sized bite out of the cylinder wall in that hole. When it finally came to rest, it shattered the valve seat, sending pieces out the exhaust and through the turbo. Pieces also traveled back into the intake manifold, where they eventually got sucked it into the other cylinder doing some damage there as well.

    Millennium Technologies, www.mt-llc.com, saved the block with some welding and replating. Their work turned out great. Due to the additional welding, cost was about $600. Lessons learned, before sending a block for repair strip it of everything. Remove the cylinder head alignment dowels, main bearing oil jets, water pump bearings, and the little plug on the oil filter base. They will take them out for you, but not for free.

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    Obviously, a new head was needed and in the process of obtaining this piece I ended up purchasing another MSX 150 and trailer that had already been partially torn down for part out. It came at a great piece and offered an unlimited supply of “spare” parts. Knowing nothing about this ski, I sent this head (and another, don’t ask separate story) to Tim at www.zforcemotorsports.com where he installed new valves, (supplied by Randy of Watcon, www.weberpower.com amongst many other odds and ends), performed a serdi valve job, and did a full inspection. Tim is a great, knowledgeable guy with very reasonable prices. He will be getting all of my 4-stroke cylinder head business going forward. It was straight forward with Tim. Box up the head and send it to him. Communication was top notch. Randy is the same. Either by phone or email these two are very helpful.

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    With major components in hand, it was off to Desperado’s site, www.precisionsports.ca to order new rods, new pistons, some bearings, seals, a PS-2M turbo, timing chain, oil pump, etc. He supplied a sweet set of JE forged pistons for the price of new stock pieces, a great deal. He also supplied massive amounts of advice on how to setup main/rod/piston clearances. He is a busy man, but he answered all my emails. Any brief wait for an answer was well worth it. He knows this engine inside out and from top to bottom.

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    A few thoughts: The Weber MPE 750 engine is by far the biggest headache I have ever touched. It has more pieces, parts, and bolts that any V8 engine produced in the 60s & 70s, but it can be rebuilt. If you are fortunate enough to be the person that tears down the unit being rebuilt, just label everything in separate bags and it will go back together a lot easier.

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    The MSX service manual is a major headache with substantial shortcomings. It is best to have a pdf copy open on a computer nearby to use the “find” function because a printed version has you jumping all over the place during assembly. It has been suggested to me that a Polaris FST snowmobile manual is a good supplement.

    Sorry to Weber and everyone that sells the specialty tools. For the most part they are not really needed. A timing chain can be cut with a $20 Dremel from Wal-Mart. Crimping a new link is a different story, although a hammer and punch appears to have worked. A metal clothes hanger and a hacksaw blade worked surprisingly well to install the new timing chain. An M20x1.5 bolt will push the mag end apart and you can spin the engine by hand or with the pto bolts. However, you will need a set of outside micrometers and a 0.0001 bore gauge to replace bearings though.

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    The final test will be to see and hear this thing run, hopefully for a long time. If all goes well, I hope to have it all together, running and tested in time to make the northeast meet in early August. It would be nice to see this stage II ecu and big turbo engine reach 70mph gps, but…

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Wow, quite the process!

    I presume an ECU reflash from PrecisionSports is also part of the new turbo package

  8. #8

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    I am going to be running Stage II ECU reflash from Desperado with the new turbo. With good gas and fresh everything, maybe it will make 180 hp, which should make an interesting ride.

  9. #9
    Mike Greenwood's Avatar
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    Ha ha

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