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Thread: 1982 r65ls

  1. #1
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    1982 r65ls

    Freshly rebuilt carbs by BING, fresh valve adjustment, carb sync, air filter, plugs. The LS starts, runs, idles fine, however, at around 4500 rpm minor hesitation.....

    Any idea what could be the fix?

    Or is this something that is specific to the R65?

    Would a different jet(s) mitigate the issue? If so, which jet(s) and what size should I look at?

    Any other suggestions?

    thanks

    jgp

  2. #2
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    Possible that you might have an airleak, or possibly a carb diaphragm isn't quite fully seated in the proper position (small tab on underside must be in little slot on inside edge of base that the diaphragm sits on). How old are your sparkplug cables? Have you replaced the original factory coil - they dark gray-colored crack-matic coils are notorious..

    Generally, if Bing rebuilt the carbs, you shouldn't need to do any messing with jets, etc. unless you are living in the Andes or maybe Rocky Mountains and didn't tell them that you are at high altitude when you sent them in.
    BMWs in my garage: 1982 R65LS, 1978 R100/7

  3. #3
    Administrator 20774's Avatar
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    A guy on another forum was having issues with hesitation on his R75/5 and did lots of things to find the problem. What eventually solved his problem (which was a hestiation around 2500-3000) was to go up one size on the main jet. I wouldn't have thought that the main circuit was in play at that low of an RPM, but at 4500, you should be well into the transition to the main jet.
    Kurt -- Forum Administrator ---> 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!

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    1982 r65ls

    Brand new OEM spark plug wires less than 2k miles ago. OEM original coil (will examine it today).

    How do I determine the next size up in the main jet. I have the BING carb book. What would the sequence of numbering for the next size up?

    thanks for the feedback

    73516

  5. #5
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    Quote Originally Posted by 73516 View Post
    How do I determine the next size up in the main jet. I have the BING carb book. What would the sequence of numbering for the next size up?
    You would really need to remove the jet and read the number stamped on it. You might not even have the right jet in there. IIRC, the jet numbers go up in increments of 5.
    Kurt -- Forum Administrator ---> 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
    Benchwrenching PGlaves's Avatar
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    Step #1 is to determine whether the stumble is caused by a lean condition or a rich condition. Take it out, transition through the stumble range a few times and immediately do a chop test and read the plugs. That should disclose whether it is going rich or lean. Probably lean but you need to know for sure.

    Then proceed with looking at the needle position and the jets to correct the mixture.
    Paul Glaves - "Big Bend", Texas U.S.A
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  7. #7
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    82 r65ls

    Paul,

    Please excuse my "ignorance", I'm not sure what you mean by, take it out, and immediately do a chop test and read plugs??

    "Take it out, transition through the stumble range a few times and immediately do a chop test and read the plugs. That should disclose whether it is going rich or lean. Probably lean but you need to know for sure".

    thanks

    Jim

  8. #8
    Benchwrenching PGlaves's Avatar
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    Ah, sorry.

    A chop test is riding along, killing the engine at highway speed, coasting to a stop, letting the engine cool down, and removing the plugs to visually observe them

    The kill at highway speed means you won't get any soot traces from idling for even brief moments, This gives the best visual observation of the plug, and mixture condition encountered by that plug.

    I usually pre-plan my destination - one that is easy to simply coast into. I've used a rest area on a two-lane highway, a convenience store, etc.

    In my earlier post I said to transition through the stumble range a few times, and then (while it is stumbling hopefully) do the chop test - meaning kill the engine.

    I would be looking for any sign of sootiness or wetness indicating a rich mixture, or no sign and maybe bright white insulator indicating lean. Absent soot or wetness I'd conclude it was lean.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  9. #9
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    Quote Originally Posted by 73516 View Post
    Freshly rebuilt carbs by BING, fresh valve adjustment, carb sync, air filter, plugs. The LS starts, runs, idles fine, however, at around 4500 rpm minor hesitation.........
    My 1985 twin-shock R65 was very sensitive to carb balance, but the symptoms would be excess vibration more than a hesitation.

    While I see that the bike "runs...fine" I do not see any mention above that the timing, and timing advance, has been checked. A good timing light and a few minutes is all a quick check takes, and should be a "must" before digging into the carbs.

    In addition, the bike needs to be thoroughly warmed up over something like a 10-mile ride for a carb sync to be truly successful. Should be checked if the sync was done on a “lukewarm” bike, and a manometer/Twin Max type tool should be used.
    Last edited by R100RT_Mark; 09-27-2012 at 04:15 AM.
    Mark

    Current - '74 TR5T : '93 R100R : '06 ST3s ~ Past - Variety of British, French, Italian, Czechoslovakian, and German bikes from the '70s, '80s and '90s

  10. #10
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    a lot of people have luck with just raising the needle one.

    My 84 recently started dong the stumble; the hall sensor was failing. Don't believe what you may hear about these electronic ignitions being "bulletproof"; I have had 3 of them go bad in 3 years.

  11. #11
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    Quote Originally Posted by jforgo View Post
    a lot of people have luck with just raising the needle one.

    My 84 recently started dong the stumble; the hall sensor was failing. Don't believe what you may hear about these electronic ignitions being "bulletproof"; I have had 3 of them go bad in 3 years.
    When the hall effect sensor went on my R65 it went from running just fine to a stutter to me being sat by the side of the road in a few heartbeats - never can tell. Decided that 25 years was a fair service period for a small electronic component subject to any number of heat cycles and other abuse.
    Mark

    Current - '74 TR5T : '93 R100R : '06 ST3s ~ Past - Variety of British, French, Italian, Czechoslovakian, and German bikes from the '70s, '80s and '90s

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