Results 1 to 7 of 7

Thread: R75/5 Repair of Stripped Cylinder Head Stud Threads in the Engine Block

  1. #1
    B Reams brook.reams's Avatar
    Join Date
    Jan 2007
    Location
    Arvada, Colorado
    Posts
    332

    R75/5 Repair of Stripped Cylinder Head Stud Threads in the Engine Block

    The first sign of the problem was this bike would not idle well. I thought the carburetors got dirty and all I needed was to clean them. But, before I started on that task, I decided to check the valves and I found the left intake valve lash was 0.012 inches instead of 0.004-0.006 inches. Hmmm .... how did that tappet get so loose?

    Before I reset the valve clearance, as I always do, I torqued the cylinder stud and head bolt nuts. But, one stud just spun. Bummer. That means the threads in the engine block are stripped.

    It turns out a friend of mine, Dick, had the same problem on his 1972 R75/5 a couple of weeks earlier. I contacted him and learned he made arrangements to rent a jig to repair his stripped threads from Northwoods Airheads. So, we jointly repaired our stripped threads in "Brook's Airhead Garage" when the jig arrived.

    This write-up is based on the work we did on both bikes.


    Here is a link to a video of how to use the Northwoods jig to drill out the damaged threads, tap new threads for a 20 mm long M10x1.5 Heli-Coil insert, and install the insert.

    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1975 R75/6||1973 R75/5

  2. #2
    Brook

    Your documentation of repairs is always first class and has been helpful to me several times. Thx much for the effort.
    Lee A. Dickinson - Danielsville, GA USA
    Airheads #3480 | Iron Butt Assn. #8914
    1976 R75/6 - 1992 R100RS - 1993 K1100RS - 2013 R1200GS

  3. #3
    Fortis Fortuna Adiuvat Omega Man's Avatar
    Join Date
    Jan 2010
    Location
    Mansfield,MA
    Posts
    13,186
    Very nice on a number of levels Brook
    I was wondering if you are a fan of making the parts “squeaky clean” before using the Locktite?
    Gary
    Last edited by Omega Man; 11-24-2018 at 01:27 PM.
    "You can do good or you can do well. Sooner or later they make you choose." MI5
    Mod Squad
    2009 F800GS 1994 TW200

  4. #4
    Registered User
    Join Date
    Nov 2009
    Location
    Central Ontario, Canada
    Posts
    324
    thanks for taking the time to do that video... I sure it will be referenced a lot... unfortunately.
    '81 R80G/S(wp4860 forks, Henderson triple clamp)
    '10 Husaberg FE450, '10KTM 250XC-W
    Past BMWs: '68 R50/2, '77 R80/7, '87 R80GSPD, '76 R60/6, '85 K100RS, '91 R100GS,'87 R100RS

  5. #5
    B Reams brook.reams's Avatar
    Join Date
    Jan 2007
    Location
    Arvada, Colorado
    Posts
    332
    Quote Originally Posted by beemerphile View Post
    Brook

    Your documentation of repairs is always first class and has been helpful to me several times. Thx much for the effort.
    You're quite welcome Lee.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1975 R75/6||1973 R75/5

  6. #6
    B Reams brook.reams's Avatar
    Join Date
    Jan 2007
    Location
    Arvada, Colorado
    Posts
    332
    Quote Originally Posted by Omega Man View Post
    Very nice on a number of levels Brook
    I was wondering if you are a fan of making the parts “squeaky clean” before using the Locktite?
    Gary
    Gary,

    Indeed, I mentioned that I cleaned the threads with acetone until my Q-tip shows no trace of discoloration indicating all the oils and grease have been cleaned off. I want to give the Loctite every advantage to reach its full bonding strength, particularly in this situation.

    When I use "blue" Loctite I always use alcohol pads to clean the male and female threads on fasteners. I get a box of them at my Walgreens pharmacy.

    Best.
    Brook.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1975 R75/6||1973 R75/5

  7. #7
    B Reams brook.reams's Avatar
    Join Date
    Jan 2007
    Location
    Arvada, Colorado
    Posts
    332
    Quote Originally Posted by grahamm View Post
    thanks for taking the time to do that video... I sure it will be referenced a lot... unfortunately.
    Hi Grahamm

    I think you are correct about this topic being referenced a lot as time goes on. Unfortunately the Haynes manual lists much too high torque settings (28-32 Ft-Lbs) for the cylinder stud and head stud nuts. The Clymer values are safer (22-28 Ft-Lbs). I'm going to settle on 23 Ft-Lbs as my standard going forward which is at the low end of the Clymer range and a bit lower than Bob Fleischer's (aka Snowbum) 25 Ft-Lb maximum recommendation.

    An interesting property of aluminum is that unlike steel, under cyclic stress, there is no stress for which an infinite number of stress cycles can occur without failure. With steel, you can keep the stress below a specific value and it will never fail under cyclic stress.

    I have wondered if this is a contributing factor to cylinder stud thread failure in the aluminum block of these bikes. Combined with using the upper range of Haynes and Clymer torque values, I suspect those higher torque values reduce the number of cyclic stress cycles the aluminum threads can take before they fracture.

    Best.
    Brook.
    Brook Reams - Arvada, CO
    Endeavor to Persevere
    Various Two-wheeled Vices, All BMW || Website: Airhead Rebuild Projects
    2004 R1150-RS||2002 F650-GS||1983 R100RS||1977 R100RS||1975 R75/6||1973 R75/5

Similar Threads

  1. Replies: 2
    Last Post: 05-21-2014, 03:24 PM
  2. Stripped Cylinder Stud
    By KALTZG in forum Oilheads
    Replies: 0
    Last Post: 03-15-2010, 06:19 PM
  3. Replies: 2
    Last Post: 06-30-2009, 11:59 PM
  4. Cylinder head threads stripped
    By enjine in forum Oilheads
    Replies: 17
    Last Post: 04-27-2009, 08:27 PM
  5. R1200RT Cylinder Head Stud Stripped
    By grw in forum Hexheads/Camheads
    Replies: 8
    Last Post: 08-10-2007, 03:39 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •