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  1. #11
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    What do you mean by "free rev?"

  2. #12

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    Quote Originally Posted by hyoctane23 View Post
    What do you mean by "free rev?"
    Basically, if I take it out of the water and run it on the trailer, then put it in, it'll run fine. Once I let off the pipes, it loses power and won't get on the pipes (around 4500rpm), until I can get the pump out of the water and the RPMs up. After that, it will run great until I let off the pipes again. Basically, it will run like crap until I can jump and then it'll run great until I let off the throttle.

    Feels very similar to it not running on all cylinders when it happens. I thought the spring was completely wrong and the needle and seat on the center wasn't opening until the RPMs picked up.

    Maybe the needles are sticking. They did look pretty worn out, but not the worst I've ever seen. edit: sticking closed, not open.

    The bad pro starts really easily too. Usually the "good pro" is a pain to start. You have to choke it to get it to fire, then turn the choke off, and if you don't get that right it's completely flooded.

    I bought the bad one as a project from someone who had the same problem, but he was clueless and thought the timing was way off (it's the same pro in the projects thread that the guy machined new holes in the timing plate to change the timing by a ton).

    The spring on the good pro being totally wrong doesn't surprise me either. I bought that from a dealer who blew it up and didn't bother torquing the engine to the mounting plate properly.

  3. #13
    Polarisitis loonatik's Avatar
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    Quote Originally Posted by hyoctane23 View Post
    The picture of the spring you posted does NOT look like a proper Mikuni spring.
    That chart appears to be correct at least for the short time I owned a Yammi with with Mikuni carb.

    Here's one just found with P/N
    https://www.blowsion.com/mikuni-pop-off-spring

  4. #14
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    I meant the picture of the spring that sdlvx posted, not the chart. The chart you posted is good except the 115 gram springs are no longer gold but shiny silver.

  5. #15
    Polarisitis loonatik's Avatar
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    Quote Originally Posted by hyoctane23 View Post
    I meant the picture of the spring that sdlvx posted, not the chart. The chart you posted is good except the 115 gram springs are no longer gold but shiny silver.
    LOL, another one of my DUH moment

    sdlvx,
    Yes, replace that spring with a Mikuni one then verify your POP in all of them. If you can't find a proper gage, a bicycle pump with gage will do fine. Just record highest reading when it pops.
    Your symptom seems pointing to flood at idle, probably needle stuck open or POP too low .... just my hunch.

  6. #16

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    sounds more like your exhaust valves are not opening


  7. #17

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    Quote Originally Posted by loonatik View Post
    LOL, another one of my DUH moment

    sdlvx,
    Yes, replace that spring with a Mikuni one then verify your POP in all of them. If you can't find a proper gage, a bicycle pump with gage will do fine. Just record highest reading when it pops.
    Your symptom seems pointing to flood at idle, probably needle stuck open or POP too low .... just my hunch.
    Your hunch on pop too low might be a winner. One of the black springs in my bucket was cut, and I pulled a black one out of the bad pro center carb. I should have marked it so I can't be sure. I never mess with the springs and always put the right ones back in. Didn't check pressure because I changed springs with the carbs on the engine. But I know they have 2.0n/s and I put the right spring in.

    Quote Originally Posted by 785 lugs View Post
    sounds more like your exhaust valves are not opening
    I will check that too. Bad connection could be telling the valves to close. Don't have time today but if the weather is good I can water test tomorrow. Would make sense, maybe the bouncing around is causing a broken wire to go between making a connection and not. Could be wrong about it with free rev and could be the bouncing around causing it to run better again. Valves work on the trailer and out of water, maybe the motor is bad and after it gets warm it stops working too? IIRC the valves will move once I get it out of the water and on the trailer, even after it was running wrong.

    Thanks guys. Been working at this thing all summer. Narrowing it down but I feel like I'm getting closer. Carbs were already trashed and filthy before I cleaned them. Previous owner spent all this time playing with timing, whining about crank being wrong, etc and doesn't look like he even bothered to go in the carbs.

  8. #18
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Did you pressure test the exhaust pipes?

  9. #19

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    Quote Originally Posted by xlint89 View Post
    Did you pressure test the exhaust pipes?
    Didn't do that either. Looks like I will do my best to water test tomorrow with the different springs in center and if that doesn't work I'll check exhaust valves when it starts to have problems. I bought it in florida but it was in Michigan for a while, pipe leak could be a problem too. If it is a leak it's a small one, I don't see any smoke inside.

    I got some stuff to check. Hopefully the rain goes away because I won't be able to play with this stuff until next week if tomorrow doesn't work out, unless I bring it back and check this weekend at my parents.

    EDIT:
    oh no I have some work. I found this post. I noticed one of the exhaust hoses between the pipe and the front collector had some odd dark stuff on it, like it was running down from the top of the hose. It's past the point where it clamps on to the collector spigot.

    The guy who had this ski before me was not good. I would have zero surprise if he left it sitting over winter with plenty of water in it.
    http://greenhulk.net/forums/showthre...=1#post2738533
    Last edited by sdlvx; 08-19-2019 at 10:23 PM.

  10. #20
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Try riding it with the seat off first. (easiest thing to do) That should allow any exhaust gas to escape before limiting RPM.

    Next check the valves and make sure they are all in sync and opening all the way.

    Last would be the pipe pressure test. Usually when the pipes cracked on me, it was internal. Allowing water into the exhaust and goofing up the whole response of the pipe. Not allowing it to reach full RPM.

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