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  1. #81

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    My pto cylinder is the one that has about 100 (and climbs slowly from 90). I can test again, but that's what I got last time. It doesn't 'feel' like a fuel delivery issue per se, but I can't be certain. The odd thing is that when it cuts out it feels just like it used to run last year on two cylinders (when I had 30 on my pto cylinder because of burn down). I get the same lowered top speed I did last year in those slowed down sections. Again, almost like that third cylinder is cutting in and out. A magneto would affect all 3 no?

    I will check and see if choke helps next time out.

    I have not ruled out exhaust into the engine compartment but not sure how to rule that out... I'm a novice here. This is already waaaaaay beyond what I thought I'd be getting into for my first engine work.

  2. #82
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    OK, well you're going to have to do some testing when it is acting up. Keep a spark or multiple spark testers on the boat. When it acts up, install it/them and see if you are dropping a cylinder.

    A magneto prob would affect all 3 cyls, but it might be a failing ignition coil too.

    Have you tried cutting the plug wires back yet?

    Yeah, try closing the choke a little and see if that improves things.

    Remove the seat. If smoke comes out, that would be an indicator. Or take a short ride with the seat off and see how the ski reacts. Be careful not to dump the ski though. It would fill up REALLY fast with no seat.

  3. #83

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    Ok. We have progress. Finally.

    I checked the pickup line in the gas tank - didn't realize it was an aluminum tube, so that wasn't blocked or plugged or coroded. I also bypassed the fuel selector (the gas line for now goes right from the filter to the fuel pump) and took the vent line off the tank in case it was plugged. And now... I have top speed!

    That said, it does studder a little *sometimes getting up to top speed, but I reliably seem to have 6400-6600 rpm. (see video here)


    Plugs still seem dry, and from what I could see of the pto cylinder, it looks clean. Might still be running a little too lean, but it's better than it was. Heating up doesn't seem to be an issue now. Choke definitely does not help - it boggs immediately, seemingly even with slight choke. I did clip plug wires yes. I also didn't see any exhaust coming out from under the seat. I didn't try a test run without the seat, but took the seat off immediately after shutting it down at the beach and had no exhaust come out.
    Last edited by nbarr7; 08-02-2021 at 12:58 PM.

  4. #84
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    That is progress. Good job.

    I'm mildly concerned about the tachometer in that video. When you go WOT, I see 6500 RPM and it starts to fall off. 6400-6300 RPM

    That is normally a lean WOT issue. I'd suggest turning your high speed screws OUT some more if you have the adjustment. Do not go more than 2 full turns OUT from a lightly seated position. If you are already there. might need to go up a jet or 2.

    UNLESS.... your piston wash is telling you that you're too rich.

    I'm also curious as to why your red light blinked for a second or 2 in that video. Were you low on oil or fuel? Other indicator would be overheat.

    Keep at it, you're doing well.

  5. #85

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    I believe it blinked because of low fuel yes. I got a low fuel warning basically immediately after this video.

    High speed screws are currently set per your suggestion a few pages ago quote:

    "Hi speed M=1 1/8 C=7/8 P=1 1/4 OUT from lightly seated position"
    Last edited by nbarr7; 08-02-2021 at 08:46 PM.

  6. #86
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    I don't think I made any screw setting suggestions other than fattening them up from factory and taking fuel out while tuning.

    I am suggesting that you go a full 2 turns out if that's where you are set at now. You might need to go up a jet size still.

  7. #87

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    I copy/pasted those numbers from post number #54 in this thread. Perhaps I mistook them as a suggestion? I only bring it up as an explanation as to where my settings are now. I can move them all to a full 2 turns if that will help certainly.
    Last edited by nbarr7; 08-03-2021 at 08:15 PM.

  8. #88
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    I see the confusion now. I posted what the book lists it at being.

    Yes, turn all 3 carbs to 2 full turns out. Hopefully your RPM will be lower from being too rich. Then you can Start turning them in to achieve max RPM. It's much safer to do this way. Running lean creates heat and causes piston damage.

    If you have any piston wash formed, keep an eye on it as that will tell how rich or lean you really are. For me, spark plugs lie. Piston wash does not.


  9. #89
    sdlvx's Avatar
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    Just an FYI, I've found that jetting for a lot of skis from the 90s isn't what it used to be, probably because fuel is not so great. I have a 90 SuperJet with a pipe, the stock jetting had a 125 main, but you'd stab the throttle from about half and it wouldn't go anywhere. 125 was what Coffman recommended long ago. I ended up with a 130 main and it runs way better.

    I also saw benefits from turning all my skis out at least half a turn from stock on the high speed. I think these manuals are more of a leanish recommendation by now as opposed to where you should be.

  10. #90

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    Thank you for the extra context. I believe my main jets are 110 currently. Can I get a pack like these and try some different settings?
    https://www.amazon.com/Pieces-Pack-C...432293401&th=1

    Or are these motorcycle and I need to buy a 115 or so from sbt for $3?
    I shouldn't really need to mess with the pilot jet right?

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