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Thread: R80RT Reacting

  1. #1
    Registered User
    Join Date
    May 2012
    Northern, Illinois

    R80RT Reacting

    My 86 R80RT recently return from a 1000 mile trip. Ran Great. Had the Carbs balanced two weeks prior, values adjusted 3000 miles ago, and it has always started immediately, (fast) and with no problem. The other day, I took it for a short trip. Drove about 150 miles and went to a gas station. Filled up and when I went to start it, it took about 3 seconds to turned over and when it did, it had a slight "spit" backfire> Never did that before. The rest of the day - no problems. This morning I pulled it out of the garage, turn the petcocks on, flipped the enricher over, and when I hit the starter, it took about 4 to 5 seconds to crank over and when it kicked on, it backfire blowing small flakes of carbon out of the exhaust. After that, no problems the rest of the day. What is my bike trying to tell me?


  2. #2
    Phil B bullfrog_28560's Avatar
    Join Date
    Aug 2012
    currently Germany
    Sounds familiar, I had to replace my pushrod seals, so I adjusted the valves because I had to. Started up quick quiet and ran great, a tank or two later I was riding through town, it just cut off on me, pulled over, went to start it and back fired loud as he.. no problems since. Have you have any back firing since? you could have had water in the gas you pumped last as well.
    Phil Bouffard
    SSG U.S. Army
    Kaiserslautern, Germany

  3. #3
    Registered User lkchris's Avatar
    Join Date
    Mar 2003
    Albuquerque, NM
    There's always a language problem with these posts.

    "Crank" means the starter motor runs, not that the engine starts.

    So, it cranked for 4-5 seconds before it ran ... as I translate it.

    On a car with a carburetor, you have a fast idle cam, on one with FI you have an idle control valve.

    You have neither on an Airhead and when starting an engine cold enough to need the enricheners, you need to manually open the throttle a bit. You don't want any vacuum leaks anywhere, either. Could still be something else, like bad gas, etc. Back fire suggests vacuum leak.
    Kent Christensen
    '12 R1200RT, '02 R1100S, '84 R80G/S

  4. #4
    No longer a member here
    Join Date
    Apr 2006
    Quote Originally Posted by lkchris View Post
    . Back fire suggests vacuum leak.
    That's a good point worth investigating!
    I ran my R100S since I revived it from a 15+ year "Sleeping Beauty" rest with the Bing rarbs slightly tilted inward. I did this, because this way, the cables were straight down into the carbs and not slightly kinked.
    The bike ran perfectly fine. I actually had to shut off the enrichener as soon as it started as it would stumble when rolling on the throttle otherwise.
    Everybody who saw it, said that it was not proper and the carbs should be perfectly vertical.
    So I changed it and turned them.
    Now I have to keep the enrichener pulled for a while until the bike warms up more and when I roll off the throttle, it backfires slightly.
    I may have created a vacuum leak at the carb boots when rotating them???

  5. #5
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    San Antonio, TX
    I don't know about being "not proper"...I've mostly heard that is what you want to do...tilt in slightly. I'm sure slightly in/out or straight up would work fine. If the cables are too short, get longer ones...I did for my /7...I believe I'm running '86 R80RT cables and there's plenty of length.

    Maybe when you turned them, you moved to a part of the carb-to-rubber tube that was hardened and the clamps can't pull it down enough such that you have a leak. Otherwise, just turning them slightly should really have made a difference.
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  6. #6
    Registered User
    Join Date
    May 2012
    Northern, Illinois
    Before writing this post, I was leaning towards a vacuum leak. When it made a slight "spit" or "sputter" sound, the first time, it appeared to come from the right carb area. I will investigate tomorrow. Thanks for all your input.

    P.S. And I will remember the definition of the word - Crank.

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