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  1. #1

    Default 15hp carb tuning

    hello
    i have finally completed assembly of my 87 15hp electric start motor. i am having a lot of problems with tuning the carb. I have completed rebuild the carb, and installed new gaskets. I have the 87 late model carb with the black plastic top cover. i even installed a new throttle roller, new neutral safety switch.
    so this is the issue.
    settings. air/fuel mix screw is at 4 turns out, set as specified
    throttle roller i cannot line up with the black mark on the timing plate, I have tried to adjust the allen head screw on the carb for the idle but i do not think it does anything.
    I need guidance on how to set the throttle roller with the black timing plate mark.
    i can start engine with choke on, after 30 sec remove choke and engine idles fine. As soon as i put in gear and give throttle the engine boggs down. no matter what setting I try it does this.
    can the timing Plate be off? is there adjustment to timing plate, or is this a carb issue
    another thing i noticed is if I hold half choke, I can rev up the engine, but with no choke it boggs down. I am thinking it is air/ fuel mixture related but I have spent close to a month tuning it and no positive results.

  2. #2
    Join Date
    Sep 2010
    Posts
    19,502

    Default Re: 15hp carb tuning

    Most carburetor problems turn out to be something else.-----What other trouble shooting has been done.-----Compression test ?---Spark test ?---Flywheel key checked ?----Reed valves checked ?----Water pump impeller replaced?----Thermostat checked ?

  3. #3

    Default Re: 15hp carb tuning

    Everything you just asked has been been tested and Reed valves clean. Brand new thermostat. Strong spark and compression. New key.
    One thing I'm still trying to figure out is timing plate. Can it be put on wrong? On my base plate I have driver's where the timing plate sits and that is where I put it back. Also I'm not really sure on how to properly perform the link and sync the carburetor roller with Mark on timing plate. I have seen just about all YouTube video on 15hp but none show actually how to adjust. I have read leroysramblings.com on carb timing. On my late 87 he said 4 turns out on the idle lean screw then once running good to set my actual idle screw which opens the roller.
    But no one shows you how to match the roller to mark .

  4. #4
    Join Date
    May 2015
    Posts
    2,172

    Default Re: 15hp carb tuning

    Does the roller have the outer covering on it? Maybe put up a pic. If the outer covering comes off of the roller you will never get it to work right. If the roller is in good shape line up the mark on the cam with the roller. You want the carb to just start opening at that point. I usually make the roller touch the cam about a 1/16" before the mark. That way when the roller hits the mark the slop will be taken out of the linkages and the carb will start to open.

  5. #5

    Default Re: 15hp carb tuning

    Quote Originally Posted by flyingscott View Post
    Does the roller have the outer covering on it? Maybe put up a pic. If the outer covering comes off of the roller you will never get it to work right. If the roller is in good shape line up the mark on the cam with the roller. You want the carb to just start opening at that point. I usually make the roller touch the cam about a 1/16" before the mark. That way when the roller hits the mark the slop will be taken out of the linkages and the carb will start to open.
    hi, yes the roller is brand new. i have rebuild the entire carb with all OEM parts,

  6. #6
    Join Date
    May 2015
    Posts
    2,172

    Default Re: 15hp carb tuning

    Maybe put up a pic?

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