96 sportster intermittent mpem recognition
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  1. #1
    Frequent Poster burton2323's Avatar
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    96 sportster intermittent mpem recognition

    So my friend and I got a 96 sportster cheap, needs top end rebuild. Having an issue with the mpem intermittently recognizing the dess key. The beeper doesnít beep, just assumed thatís old and bad. Have had plenty of Sea-Doo buzzers go on me.

    the oil tank is low, so when the key recognizes the light will stay on. 7/10 times light comes on for ~1 second then goes off. (Assuming this would be one long beep saying mpem does not recognize key)

    taking key off and trying again will sometimes do same thing, and sometimes allow starter switch to start engine. Iíve ran the big ground from the ground post in big gray box to neg terminal, and cleaned the grounds making sure good contact.

    All 3 15a fuses on the mpem are good, and the 30a fuse is blown. (I donít think that will effect this though, as thatís for front fuse block power.) I know the key is programmed right as sometimes it works.

    quite stumped here, and itís driving me nuts. Any thoughts or suggestions where to start? I appreciate any help in advance. Thank you

  2. #2
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 96 sportster intermittent mpem recognition

    Try another DESS post.

  3. #3
    Frequent Poster burton2323's Avatar
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    Re: 96 sportster intermittent mpem recognition

    Haven’t tried cleaning that yet.. will do tomorrow

    If it were to be a dess post would I be able to test and prove it? I know when you have 12v across one wire mpem turns on and a low voltage signal gets sent across the other wire enabling ignition and limiters

  4. #4
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 96 sportster intermittent mpem recognition

    There is no cleaning.....the best test I know is a known good one.

  5. #5
    Frequent Poster burton2323's Avatar
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    Re: 96 sportster intermittent mpem recognition

    New dess post ordered. Will report back!

  6. #6
    Frequent Poster burton2323's Avatar
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    Re: 96 sportster intermittent mpem recognition

    Okay question #2...

    So I rebuilt the top end with wsm stock bore, and I’m getting exactly 80psi in each cyl. I can feel a tiny pulse of air coming out the base gasket at the pto. Won’t hold an idle, but with 1/8th throttle it will stay running. Not perfectly smooth but running.

    Do people normally supplement the base gasket with rtv? I know the rings are right, in their notch and the cup is on the top facing up. Both cyl walls felt and looked fine. The crown on the mag piston was blown apart when we got it, and had 0psi in that cyl

  7. #7
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
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    Re: 96 sportster intermittent mpem recognition

    Cant have air leaks......

  8. #8
    Frequent Poster burton2323's Avatar
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    Re: 96 sportster intermittent mpem recognition

    I have a feeling I screwed myself by going stock bore.

    Both cylinders are exactly 80psi, would a small leak on pto base gasket cause that?

  9. #9
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    Re: 96 sportster intermittent mpem recognition

    Base gasket leak wont affect compression.

    A 720 wont run at 80 psi your gauge is bad. To do it right you should bore the cyls....I would go .50 oversize to clean out any egg shape the cyl probably has.

  10. #10
    Frequent Poster burton2323's Avatar
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    Re: 96 sportster intermittent mpem recognition

    Before I tore the engine down mag cyl had 0psi and pto 125. The engine ran but clearly on one cyl. This tells me, at least the pto cyl, would be operational. (Still planning on boring .50 over just trying to wrap my head around this.)

    What would/could cause me to now have identical, but not adequate compression in both cylinders? My gauge is probably not the best, had it for a while, but assuming seeing 125-130ish is a decent reading. If a 720 won’t run on 80 and that’s what’s I’m showing now, it’s probably more like 100 each hole, or whatever minimum compression needed to run would be. As soon as throttle drops below ~15% it dies out. All on the hose, just this afternoon.

    What could I of done wrong? Shouldn’t the cyl that was reading 125 before at least be at the same compression level?

    I appreciate the help. Truly

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