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  1. #1

    Max 4000 RMP after "new" engine

    Del might be able to add more to this, but here it goes:

    We put a new bottom end in my 900 after I spun a crank bearing. The bottom end came from a 1050 and all the top was from my 900. We quickly found that the 1050 and 900 cranks are not the same and ended up having to swap the 1050 cdi to get her to run. She seemed to run fine on the trailer after that.

    I finally got around to doing the break in the other day and everything was fine at the beginning until I tried to finish with a couple WOT runs and found that I couldn't get past 4,000 rpm in the water...about 27 mph tops.

    I snipped the tan wire at the MFD and even tried a run with the MFD disconnected to rule out the rev. limiter but no change. I'm a little stumped here.

    Any suggestions?


  2. #2
    Curious! What year? did you check compression? and is the crank known to be good? and in index? Z

  3. #3
    ph2ocraft's Avatar
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    You want to disconnect the grey wire to the CDI, if applicable for your year model.
    Last edited by ph2ocraft; 09-24-2006 at 04:03 PM.

  4. #4
    Moderator beerdart's Avatar
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    PH your PM box is full!!!!

  5. #5
    ph2ocraft's Avatar
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    LOL I just emptied it again

  6. #6
    Hmmm....gray wire? Hmm...now I'm curious. Guess I better go check which one I cut!

    Compression was at about 119, crank and index are believed to be good.

  7. #7
    Cool! what year? Z

  8. #8
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    Guys I just rode it a while ago.
    At the moment, it still has premix from the break-in, and possible fouled plugs.

    We replaced the crank on this with a 1050 crank, so I'm guessing it'll need a timing adjustment.

  9. #9
    2&4strokepolaristech's Avatar
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    not revving past 4000

    is that crank rebuilt or used? if used was it ever rebuilt before and if so did the boat it came out of run good? the reason that i ask is two.
    1st is that i have seen many of non-polaris guys rebuild cranks and when they reassemble them they do not phase them properly. 2nd is as mentioned above please make sure that crank is within a good index. this can be dome with venier calipers or a dial gauge that is made to time two stroke engines. have you compression checked it? always start with a compression gauge(I call it taking the engines' blood pressure that is what they always do the first thing when you go to the dr's right LOL)

  10. #10
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    This was a good lower half from a used 1050. Never locked or twisted.

    This has 900 cylinders with a 1050 cdi, it was the only way it would run.

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