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  1. #1

    Idle Adjustment 99 Yamaha 1200 XLL

    Yamaha 1200 PV motor w/ stock Mikuni carbs. Motor idles right around 1000 rpm. When I turn the adjuster no response is noticeable at first then it goes to about 3000+ rpms. Just rebuilt the carbs, took it for a water test passed w/ flying colors except for the idle speed. Took the carbs back out, disassembled them to see if anything was incorrect, but it all looked good. Reassembled only to have the same problem. Any ideas? As you know the whole exhaust system has to come off to get to these carbs so adjusting them while running is difficult. These carbs also have sealed high & low speed adjustment screws which some mechanics drill out to adjust. I have'nt had to do that yet as all the carbs that I've rebuilt have worked out well. Your help and advice would be greatly appreciated. Aloha, Mel @ North Shore Watercraft Service.


  2. #2
    Happily Self-Employed WFO's Avatar
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    are you using the factory remote idle adjuster?

    I have seen the remote adjustment cable get streched and rusted up internally and do this... you have to crank a bunch to get it to move a little

    I usually crack the throttle open a smidge while adjusting the idle so the idle adjust cable doesnt have to move the return spring

  3. #3

    idle adjustment 1200 XLL

    Actually I've replaced it w/ another one just to see if that was the problem. It is fully lubed so I don't think that's the problem. Thanks.

  4. #4
    Happily Self-Employed WFO's Avatar
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    I usually crack the throttle open a smidge while adjusting the idle so the idle adjust cable doesnt have to move the return spring
    did you try this?

  5. #5
    I just did. Idle seems to get worse as I turn it in till it dies. Did'nt check pop off. Replaced N+S & installed the only spring that comes w/ the Mikuni "I" rebuild kits for Yamaha which is the bright silver one. About ready to remove carbs again to do pop off check unless you have any other ideas. Is pop off check part of every rebuild? I've only done it if the rebuild does'nt solve the problem. On non PV motors it's not so bad but w/ these motors, it's another 4hr. min to remove, test then reinstall. Or just include the extra hr. on the original rebuild job. Thanks

  6. #6
    All hail the Chief! fullboogie's Avatar
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    You should always check popoff. Sometimes the wrong springs are included in the kit, sometimes the psi is just way off and needs adjusting.

  7. #7
    Thanks. Having trouble keeping the hose in the fuel inlet orifice. I read that to get an accurate reading the pump bodies have to come off. Bought a Pressure gauge from SBT. Difficult to get it to 60lbs. Just ordered a Mikuni gauge which goes up to 100lbs. Any tricks on attaching the gauge hose to the carb?

  8. #8
    All hail the Chief! fullboogie's Avatar
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    Zip tie? Clamp?

    I've not ever taken the pump bodies off to check popoff.

  9. #9
    Thanks for all your input & advice. Turns out the low speed screws had been screwed in all the way from the last rebuild. They had been covered w/ grease so I just assumed they were still factory set. Backed them out to factory specs & installed the gold springs rather than the bright silver one that came w/ the Mikuni rebuild kit. Started right up & was able to adjust idle & get snappy response from throttle.

  10. #10
    All hail the Chief! fullboogie's Avatar
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    SEE???!!!! All you have to do is listen to us! Go ahead and admit it - this forum rocks. It's ok, you can say it.

    By the way - did you check popoff? Or did you just install different springs and call it a day?

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