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Thread: Stuttering at speed, R75/5

  1. #1
    Club President HankPfister's Avatar
    Join Date
    Mar 2003
    Location
    Blue Ridge Mountains, Virginia
    Posts
    323

    Stuttering at speed, R75/5

    Hey folks,
    I have a R75/5 that is in good tune, starts and runs great, except for a stutter at around 70mph. In 4th gear as I'm gradually accelerating as the bike gets to about 4200 rmp and 70ish mph it stutters a bit, then gets past it and keeps on accelerating. Same thing will happen at slower speeds if I wack the throttle open suddenly.
    Where should I look next? Carbs have been cleaned, valves set, points and timing set, new plugs, and new plug wires.


    Thanks for some help.
    Hank Pfister
    Copper Hill, VA
    pfestus1@yahoo.com
    2007 R1200GS, 1973 R75/5/Dnepr, 1984 R100RS/Motovation.
    www.twinvalleyriders.com

  2. #2
    Registered User
    Join Date
    May 2012
    Location
    VA
    Posts
    248
    It sounds to me like a carburetor problem. If it were my bike, I would be focusing on the needles, jets, and carefully examining the diaphragms - and probably clean the carbs (again). Good luck!
    Stan

    AH# 13238

  3. #3
    Registered User lmo1131's Avatar
    Join Date
    Jan 2010
    Location
    Pismo Beach, CA
    Posts
    2,923
    You didn't mention if the bike was doing this before you changed plugs, etc. (I'm assuming it did not)

    If it was, did you check the diaphragms when you did the carburetors?

    If not, are you running inline fuel filters? Replace them, with the thought that perhaps they aren't passing sufficient fuel at the given rpm.

    It would not be the first time a bad spark plug made it passed QC. I fought a "stutter" in my Karmann Ghia (also an airhead) for about two weeks before I identified the problem as a defective plug. On the flat it would run like a champ, but up any of a grade it would start to miss... a minute crack in the insulator.
    "It is what you discover, after you know it all, that counts." _ John Wooden

    Lew Morris
    1973 R75/5 - original owner

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