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  1. #1
    urugol's Avatar
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    Picked up another 900 today

    Got this thing for a song. It's a 97 just like my other one and the deal was too good to pass. Technically I paid about the value of the trailer and registration so I consider the ski a freebie.

    Initially I looked at this as a spares machine for my other one, but I'm thinking I will freshen the top end so I have 2 and don't need to stress rushing my pro build. This dude had a serious lean piston seizure, check out the pics. Interestingly it is running premix

    I comp tested the centre and pto and got 115/110 but I did a quick test by just fitting the domes - is this close enough to be valid or should be done with exhaust on etc?

    Also took some pics of mag jug where seizure happened. Any thoughts on re-use/boring to oversize should be ok? Or do I get another jug?

    I have a new set of hot seat domes setup for 92 octane I bought a while back, could put those to good use now as well.
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  2. #2
    bowsniper's Avatar
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    Nice! A twin...That ski is in great shape. wow. looks new.. maggie looks a little worn.lol 120 or so would be better for compression..

    I would clean the case and see whats in there anyways if anything.. looks like the carb on the pto stopped delivering fuel huh? man, thats total destruction right there. never seen one that bad.

    wide open throttle, good compression gauge with air release at gauge, strong battery,10.6 or higher voltage for cranking, 3 checks per cylinder, cold,no oil in cylinder, check head bolts and base nuts for proper torque on them. 5 rotations per test.

    I would get another jug,piston,rings,roller bearing,circlips for the one cylinder and re-ring and hone the rest.. Just my opinion..

    Wash looks fine in the center for rec riding, mag is a tad lean IMO.

    Good find..Congrats.. Definitely go thru the usual's...carb rebuild, fuel lines,ete..... Now put that away and finish your Pro! You can play with that later! lol

    I bet the last time he rode it, it sounded like a diesel! knock,knock,knock.....ping ping ping..

  3. #3
    urugol's Avatar
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    Yeah I'm thinking the same, just get another piston/jug and re-ring the lot. Apparently the guy told me he was pulling 2 tubes going unreal when he lost power. His speed dropped down to like 30mph - it was still running on 2 cylinders

  4. #4
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    i'd pressure test the crankcase,bet the front seal leaks

  5. #5
    bowsniper's Avatar
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    Check the indexing of the crank too. severe detonation in that cylinder could indicate a crank out of index..Maybe the ski was swamped or got water in the carbs and threw it out of index. Just a possibility anyways.. wouldn't hurt to check it out.

  6. #6
    urugol's Avatar
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    I removed the carbs on this thing today while I was letting another base coat dry on the pro outside - to take a look and the condition of the mag carb in particular where the burndown occured. the interesting thing I noticed is that there are no high screws (it is premix so they are not needed is that right?). What was more interesting was that the low screw could no be undone, it was like welded in there. I could feel the head of the pin was about to snap as I turned it with a flathead screwdriver so I'm thinking this was never adjusted or checked for wash pattern. I had to use multigrips and some wd-40 it took some work to take it out. So I'm wondering if perhaps it was not adjusted for the correct amount of fuel, and the piston was starved then burnt itself down. Any opinions on this hypothesis? I should also mention the reeds on the mag are super stiff, in comparison with the ok pistons they have a nice flex to them.

  7. #7
    bowsniper's Avatar
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    it must have adjusters somewhere. premix has nothing to do with that. no high speed adjusters? are u sure? Any pics of the carbs up close? what kind are they? stock stuff?

  8. #8
    urugol's Avatar
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    Stock Keihin CDK II's. I'll post up some pics shortly.......

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by urugol View Post
    Stock Keihin CDK II's...
    Quote Originally Posted by urugol View Post
    ...condition of the mag carb in particular where the burndown occurred. the interesting thing I noticed is that there are no high screws (it is premix so they are not needed is that right?).

    Pre-mixed oil+gas does not mean there is no need for correct high-speed fuel:air mixture.
    In the stock Keihin carburetors all high-speed adjustment is done by changing the jets. There is no adjusting screw for the high speed circuit.


    What was more interesting was that the low screw could no be undone, it was like welded in there. I could feel the head of the pin was about to snap as I turned it with a flathead screwdriver so I'm thinking this was never adjusted or checked for wash pattern. I had to use multigrips and some wd-40 it took some work to take it out. So I'm wondering if perhaps it was not adjusted for the correct amount of fuel, and the piston was starved then burnt itself down. Any opinions on this hypothesis?

    The Low Speed adjustment would not greatly affect high speed fuel delivery. The stuck screw may indicate that the carbs have not been serviced in a long time (or never) and may be internally clogged.


    I should also mention the reeds on the mag are super stiff, in comparison with the ok pistons they have a nice flex to them.
    If the reeds seem bad, change them out.

    The Keihin carburetors are internally more complex that the Mikuni SBN. When they are operating properly you get better fuel economy and smooth operation across the power range.

    Flip side is that they are harder to tune for non-stock configurations, since everything is done with jet changes.

    I think you can have the Keihin CDK II carbs modified to install high-speed adjusting screws.

    All Polaris carbs are factory/stock adjusted for oil injection. Changing to pre-mix means a small percentage of the fuel is displaced by the oil, so pre-mix causes a slightly leaner fuel delivery into the engine. Often the difference is minor, but on the Keihin's with no adjustment you either live with the slightly leaner operation or you adjust the jetting.

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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