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Thread: 1982 R100RS runs erratically after 2 miles (warmed up)

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    Question 1982 R100RS runs erratically after 2 miles (warmed up)

    As thread title states, my 1982 R100RS is running erratically after 2 miles. What happens is the bike runs fine until it warms up and then starts to "lurch" and run erratically. What I have done so far is: opened and cleaned Bing carbs...twice...the second time installing new o-rings and gaskets. I've checked timing, valve clearances, run compression test, checked fuel lines. My next diagnostic suspicion is choke linkage, but I am wondering if anyone can steer me in directions I haven't considered. Diagnostics have never been my strong suit.

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    '99 '03 '06 National Co-Rally Chair Friedle's Avatar
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    Have you checked/considered the heat sink paste on the back of the ECU located under the gas tank on the backbone on the right side. Lack of paste or dried paste can cause the above problems.

    Friedle
    Ride fast safely

  3. #3
    Registered User Guenther's Avatar
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    Sounds like the enricher is not closed when the motor has warmed up.

    /Guenther
    2017 F700GS

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    Electronic Ignition Updated

    Quote Originally Posted by Friedle View Post
    Have you checked/considered the heat sink paste on the back of the ECU located under the gas tank on the backbone on the right side. Lack of paste or dried paste can cause the above problems.

    Friedle
    I liked your suggestion and got under the tank at the ECU where I had applied heat sink paste in the past. My original Hall canister and ECU were replaced (by me) in 2016 with the Alpha Ignition System v.3 from Motorrad Elektrik (Rick Jones). The Alpha ECU is closed and doesn't require periodic maintenance...I checked this with Rick Jones and he confirmed. Thanks for your suggestion!

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    Quote Originally Posted by Guenther View Post
    Sounds like the enricher is not closed when the motor has warmed up.

    /Guenther
    Thanks, Guenther...I have been thinking along the same lines and that's where my work is headed next. I'll let you know how it goes.

  6. #6
    Registered User lkchris's Avatar
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    Did your carb work include new diaphragms?
    Kent Christensen
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    '12 R1200RT, '02 R1100S, '84 R80G/S

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    Quote Originally Posted by lkchris View Post
    Did your carb work include new diaphragms?
    I did not put in new diaphragms...they were not worn, torn, etc.

  8. #8
    Registered User STEVENRANKIN's Avatar
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    Choke

    Did you recheck your choke function/settings?

    What have you found or eliminated? St.

  9. #9
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    Thumbs up 1982 R100RS running well now.

    My original problem of the bike hesitating after 2 miles got better when I epoxied the dome inserts on both CV carburetors. I did both, but I think the problem was on the right carb where the dome insert was discolored (brown). Robert Fleischer mentioned in a tech article that if one or both dome inserts leak (air), the bike will run as though the diaphragms are torn. After epoxy sealing the dome inserts, the RS began to do better after 2 miles, but still had intermittent hesitation issues. That got resolved when a friend suggested I check spark plug wire connections. It turned out I could not pull the left side plug wire out of the coil and when I tried to loosen it a bit with a small twisting motion, the wire separated from the copper connector on the wire's end. The connector remained in the coil. When I put a replacement wire in left coil, the bike has been tip-top ever since. Looking back, I believe I had multiple issues that required cleaning/repair of the carburetors and replacing my spark plug wires.

  10. #10
    Liaison 20774's Avatar
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    Thanks for the feedback! Guess the old adage of going back over everything that was touched still is a wise thing to remember.
    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!

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    Registered User STEVENRANKIN's Avatar
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    Thanks for the information

    Thanks for taking the time to let us know what you found. St.

  12. #12
    Registered User Anyname's Avatar
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    Plugged vent in the fuel tank?
    BMW R bike rider, horizontally opposed to everything...

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