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  1. #1

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    Stock Pro 785 Carb Springs?

    I hate to be a lazy s**t but I enjoy not having cuts all over my hands. I am working on a second pro, it seems to want to sputter and have problems, like it's running on two cylinders, if you let off the throttle. It won't run right until it starts to free rev and then it will run right.

    I've been thinking about a lot of possible causes. I went through the carbs a week or so ago, and noticed that all the springs for the needle were the same size. I haven't been in the carbs on my running pro 785 in a while, but I thought I remembered the center one being significantly shorter than the outside carbs.

    Tried looking up the part number and there isn't one in the parts diagram. Anyone know off hand what spring goes on the center carb stock? I could have sworn it was some smaller, really stubby one, and that all three springs are not supposed to be the same. I don't even need to know exactly what it is, if I know it's different I'll take the good one to the Mikuni guys by me and have them get me one. I just want to know before I go pulling carbs apart, only to end up wrong because of bad memory.

    Thanks for saving me from chopping up my hands getting those carbs out.

    I swear the two on the outside are the same springs and the one in the middle is different but it's been so long. I appreciate it if anyone knows off hand.


  2. #2
    Polarisitis loonatik's Avatar
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    Feel free to browse my collection of Polaris carb settings (in signature below)

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  4. #3

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    Thanks loonatik, I have the service manual and the spring rating for the 98 pro 785 is missing, it just gives pop off pressure.

    I took my good pro apart, the bad pro had a black spring in it. The good one had a really short, soft spring. I went to put the good one into bad pro and I managed to lose the spring.

    Where do you get these springs? I looked at Mikuni parts numbers and they don't seem to have any that small. I can go see a Mikuni dealer Tuesday and ask for his advice but I'm not going to be able to play with these things for the rest of the week, going to drive me nuts.

    EDIT: I found it, it's a Keihin CDK spring.

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  5. #4
    Polarisitis loonatik's Avatar
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    The 99 and 2k pro call for 80 gr. Carb settings for them include your 98 are the same, so you can safely assume 98 is also 80 gram (black) spring.

    As long as you achieve correct POP, it really doesn't matter what spring you use.

  6. #5

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    I don't understand why my good pro has always had a smaller spring in the center carb.

    I know the bad one had the blacks in all 3 carbs, and it's never ran right. As soon as I let off the gas after it gets going it bogs and runs very poorly, like on two cylinders, until it can free rev. I was thinking the pop off was wrong and when the other two cylinders can free rev it can raise the pressure enough to open up the needle and get it to run right.

    Both are 98s. Guess I need a tester or something. The guy who had the bad pro before me was a total tool and had zero idea what he was doing. I just thought I was on to something when I saw the springs were different.

    Does the three black spring setup use 2.0 needles and seats in all carbs?

  7. #6
    Polarisitis loonatik's Avatar
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    Per above chart, if you have 2.0 needle then 65 gram spring is what you need to put POP in range.
    However, POP setting in service manual only applies to factory settings. For example, if you put larger pilot jet in then you'll need higher POP than suggested setting in the manual.

    Go through your current carb set up and list them here so we have a baseline to start with.
    Main Jet: ??
    Pilot Jet: ??
    High screw: # of turn?
    Low Screw: # of turn?
    POP: ??

  8. #7
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    The picture of the spring you posted does NOT look like a proper Mikuni spring.

  9. #8

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    Quote Originally Posted by loonatik View Post


    Per above chart, if you have 2.0 needle then 65 gram spring is what you need to put POP in range.
    However, POP setting in service manual only applies to factory settings. For example, if you put larger pilot jet in then you'll need higher POP than suggested setting in the manual.

    Go through your current carb set up and list them here so we have a baseline to start with.
    Main Jet: ??
    Pilot Jet: ??
    High screw: # of turn?
    Low Screw: # of turn?
    POP: ??
    Everything is stock.

    155 main on mag and PTO, 150 on center.
    105 pilot
    high speed 0 out
    low speed 1 turn out
    2.0 needle/seat

    I've had my good pro for 10+ years and it's always had that spring in it. I never changed it when rebuilding because the rebuild kits never came with that size spring and it ran fine.

    Quote Originally Posted by hyoctane23 View Post
    The picture of the spring you posted does NOT look like a proper Mikuni spring.
    I don't think it is, I looked online and I couldn't find one from Mikuni that looked like it. It's probably about half the size of the silver one, and it's very squishy. But it's a pro and sometimes it does things non-standard. I thought maybe the pop off would be different on the center because of how the carbs are set up with two pumps and the center getting all the leftover fuel. Like it would have different pop off springs because it's already getting pressure from the mag and pto carbs.

    So no one runs a short spring like this in their center carb on their pro?

  10. #9
    I'D RATHER SWEAT THAN SHIVER hyoctane23's Avatar
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    They all should be the same spring and N/S. I believe the Pro uses 65 gram springs stock. I know that one chart shows 80 gram springs but they probably did that in an effort to stop the carb from dribbling at a sacrifice for a little less throttle response. You need to have a relatively low pop off to have the crisp throttle response on these boats but it can make it hard to start sometimes.

  11. #10

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    Guess I'll try a shiny silver today. Took a black one out, but I guess that's not my problem with the loss of power until it free revs if people are running blacks and not having problems.

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