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Latest post Thu, Apr 20 2017 2:04 PM by JAMES.DEAN. 3 replies.
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  • Mon, Apr 17 2017 9:06 PM

    71 sporty with mikuni vm carb setup?

     Hey everyone. i recently picked up an 71 sporty that i added a mikuni vm 38 round slide. my problem is it came with no instructions on how to set the initial thing up. i installed it and it does run but doesnt seem to be right. does anyone know where i should set my initial air screw and idle screw? i havent found anything online for how to set it up. when its running right now it seem to be idleing high but twisting the idle screw doesnt seem to make anything really change unless its like going 3 turns in or out and likewise my air screw doesnt change anything. am i missing something?

  • Tue, Apr 18 2017 6:09 AM In reply to

    • FX
    • Top 10 Contributor
    • Joined on Sun, Mar 12 2006
    • Tonawanda NY
    • Posts 5,206
    • Moderator

    Re: 71 sporty with mikuni vm carb setup?

    I don't know much about your carb, but in general you would start at 1 1/2 turns out on idle air screw, then screw it out, and in with it idling till you get the smothest idle. The idle screw you're talking about is probably idle speed.


    Don't force it, get a bigger hammer.

  • Tue, Apr 18 2017 3:31 PM In reply to

    • Ironhead
    • Top 10 Contributor
    • Joined on Tue, Mar 21 2006
    • Near Sunset at Sunset Beach, O'ahu, HI Oct 23, 15
    • Posts 2,659
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    Re: 71 sporty with mikuni vm carb setup?

    blake - first, welcome to the forums - what part of the country are you from?

    a quick google search found the home page for mikuni - http://www.mikunipower.com/ - they appear to have some tuning manulals listed on their site.

    Hope this helps

    The first tool out of the box should be the "book"  Geeked

  • Thu, Apr 20 2017 2:04 PM In reply to

    Re: 71 sporty with mikuni vm carb setup?

     http://www.mikunipower.com/Manuals/VM_Manual.pdf is a manual from Mikuni on how to set up and tune these type of carburetors. The idle screw moves the slide up and down which changes the idle so if when turned it does not change then something is wrong and would take the top off and inspect the piston and idle adjusting screw. If there is anything further I can help with please reach out and ask.




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