R80 Butterfly Screws - HELP

Discussion in 'Airheads' started by CNRED, Apr 17, 2018 at 1:40 PM.

  1. CNRED

    CNRED It'll be OK

    Joined:
    Feb 17, 2008
    Oddometer:
    712
    Location:
    Scottsdale, AZ
    Last year I bought a 1984 R80st. Bike had about 85k showing, but had documentation dating back to warranty work in 1985, it came with it's own 3-ring binder of records. Along with the records were a boat load of extra parts and cables some new, some parts, some used, none the less all came with the bike. The bike had sat for a few years before the previous owner decided he was ready to part with it.
    Unfortunately, it was not stored properly, so the carbs and other systems needed to be refreshed. I ordered a carb rebuild kit from Bing Carbs to include gaskets, o-rings, needles and needle jets. While waiting for the kit to arrive, I started going through the cadre of parts that came with the bike and noticed that the PO had ordered Bing rebuild kits three times in the past as well. The Bing plastic bags were in the extra parts cash.
    Each if the three plastic bags contained two o-rings and four Butterfly screws. I thought it odd that most likely over 85k miles and three carb rebuilds, no one replaced the Butterfly Shaft O-Rings. I pulled the carbs and relized the problem right away.
    It seems that at some point, most likely during the first carb overhaul, someone mangled the Slotted Screw heads of the Butterfly Shaft to the point the screws can not be removed with a screw driver.
    Does anyone have a sure fire method to remove these damaged screws? I certianly do not want to have to buy new Throttle Shafts to remedy this problem.
    I'm sure the Throttle Shaft O-rings have not been changed since 1984, my logical mind is telling me they probably need attention.
    ANYONE?
    #1
  2. Big Bamboo

    Big Bamboo Aircooled & Sunbaked

    Joined:
    Sep 29, 2010
    Oddometer:
    12,758
    Location:
    Big Island of Hawaii
    If there is significant play in the throttle shaft to carb body, the shafts are likely worn and will need replacing... They aren't THAT expensive! :D From Disston:
    "The tiny screws that hold the butterflies in the throttle shafts are peened in place. They have been deformed with a punch and hammer so they won't come out. You have to cut or grind the far end of the screws where they are staked. I think the cool way to do this these days is with a Dremel tool using a tubular grinder. (BB had something neat about this, did I get it right?) You will need new screws and if you mess up the screw removal you may need new shafts (I had to replace one last year because I messed it up).

    New screws can be installed with Loctite so staking isn't required. The butterflies are marked with a small dot or dimple on the outer face top half. If the mark is not visible mark it with a felt pen or something."
    #2
  3. chasbmw

    chasbmw Long timer

    Joined:
    Feb 19, 2006
    Oddometer:
    3,181
    Location:
    Bath Uk
    It’s very easy to but the butterflies in the wrong way round


    Sent from my iPhone using Tapatalk
    #3
  4. daveoneshot

    daveoneshot Been here awhile

    Joined:
    Dec 14, 2010
    Oddometer:
    558
    Location:
    Vermont
    A little flat file can be passed over the peened screws, gently, and with patience. I think there's a flat surface milled onto the shaft .....makes a nice guide.
    #4
    cwroady likes this.
  5. CNRED

    CNRED It'll be OK

    Joined:
    Feb 17, 2008
    Oddometer:
    712
    Location:
    Scottsdale, AZ
    I've removed butterflies in the past, I've always used a small file to take the peened end down a little. Never had an issue. I inhearted this problem, now I'm trying to determin how to remedy the problem.
    The throttle shafts don't seem to be loose or sloppy in any way. My concern is that the Throttle Shaft O-Rings have most likely never been changed. In order to do so the butterflies have to come out. With the damaged screw heads, short of very carefully drilling them out, I'm not sure what alternatives I have.
    @Big Bamboo, where did you get your replacement shafts? Are throttle shaft o-rings really worth worrying about? I'd feel better and all warm and fuzzy if I could find a way to replace them.
    #5
  6. Big Bamboo

    Big Bamboo Aircooled & Sunbaked

    Joined:
    Sep 29, 2010
    Oddometer:
    12,758
    Location:
    Big Island of Hawaii
    MaxBMW :
    13 11 1 336 585 SHAFT $10.35
    [​IMG]
    #6
  7. disston

    disston ShadeTreeExpert

    Joined:
    Mar 22, 2011
    Oddometer:
    14,028
    Location:
    Silver Spring, Md
    I could not get the screws out once and decided to cut the throttle shaft to remove it. This has the advantage of being a way to pay back the part that has pissed me off by destroying it. I have a handle that fits sawzall blades and I used this blade with the handle.

    [​IMG]

    https://www.amazon.com/Bosch-RSM418-5-Piece-Scroll-Reciprocating/dp/B000FAKY3I/ref=sr_1_44?
    s=hi&ie=UTF8&qid=1524089687&sr=1-44&keywords=sawzall+blades

    It is a difficult blade to find. My hardware store didn't have it and searching it only shows up on page 2.

    Here is a link to a similar handle that uses sawzall blades.

    https://www.amazon.com/MK-Morse-JSH...24090003&sr=1-2&keywords=sawzall+blade+handle
    #7
    atlthrux likes this.
  8. airheadPete

    airheadPete Wherever they send me.

    Joined:
    Nov 5, 2012
    Oddometer:
    1,250
    Location:
    Portland, OR area
    Glorious quote!
    Fabulous, Disston! You’ve put into writing what we all feel and do occasionally. :thumb
    #8
  9. tennessee thumper

    tennessee thumper Long timer

    Joined:
    Nov 3, 2007
    Oddometer:
    1,300
    Location:
    Arkansas Ozarks
    For what it's worth. I replaced the shaft, o rings and screws---to be sure--when I did mine a few years back.

    I did not know any better on the front end and buggerd up the shafts removing the screws. Replacement parts were nominal, all things considered and I did a full rebuild on all the butterfly parts, sans the actual butterfly.

    Of note, make sure that the butterfly is seated properly by holding it up to a light source-when its closed.
    I put mine in with correct orientation but one side was "just off". Took me a minute to figure that out when I was having an issue getting the idle set. Had to open em back up to notice the one butterfly was slightly askew. Proper seating solved the idle issue.
    #9