Results 1 to 15 of 36

Thread: Ran into a nasty issue with the cylinder head mounting stud

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1

    Unhappy Ran into a nasty issue with the cylinder head mounting stud

    Hey All,

    Long time owner just getting back into riding.

    I am in the midst of rebuilding the heads on my 1972 R75/5. Today I finished work on the left head and was torquing everything in place (the 4 rocker arm nuts and the 2 cylinder head nuts). I am following a guide which specifies the following:

    The sequence I tighten the nuts in is 2:00, 8:00, 4:00, 10:00, 6:00 and 12:00. The stages I tighten the nuts are 10 FOOT/pounds, 15 FOOT/pounds, 20 FOOT/pounds, 27 FOOT/Pounds.
    On the 15FOOT/pounds set something odd happened with the nut at 4:00... it kept spinning. Before I thought about it I gave it a couple of turns... crap. Now the bottom right cylinder head mounting stud appears to be pulled out a few millimeters. So yeah I got that sinking feeling that the stud is pulled out of block. I have no idea what else it could be... I suppose I need to tear the head back down and see what is going on.

    So assuming this is the case, what do I do with a stud that gnarled the block? How do I reinstall a new stud when the threads are most likely screwed (and be sure it can withstand 27FOOT/pounds)? I am worried I hit a land mine here...

    Here is a photo of the rocker arms, you can see how much first the bottom stud is than the top stud. The top stud is torqued at 15 FOOT/pounds. The bottom was at 10 FOOT/pounds but will keep spinning with the wrench set at 15 FOOT/pounds:


  2. #2
    Fortis Fortuna Adiuvat Omega Man's Avatar
    Join Date
    Jan 2010
    Location
    Mansfield,MA
    Posts
    11,917
    Welcome to the forum!
    Chances are you will get some info tomorrow when more members are on. It seems to me that this has come up recently, Kurt will probably remember.
    Good Luck.
    Gary
    "You can do good or you can do well. Sooner or later they make you choose." MI5
    Mod Squad
    2009 F800GS 1994 TW200

  3. #3
    Registered User dieselyoda's Avatar
    Join Date
    Mar 2013
    Location
    Winnipeg, MB, Canada
    Posts
    1,211

    I can't answer specifically to your R75/5 but,

    I have a story, not a good one. There was an engine that came on the market that was quite a bit different than the usual old iron. The torque specs for the cylinder head bolts was way too high. I was very fortunate to be the first guy to do a cyl head on this particular engine and extremely lucky to be able to hone my craft with this engine about 40 miles north of the Arctic Circle, in the winter.

    My engine did exactly what yours is doing now. Fortunately, I had 30 of them, 18mm in diameter to mess with. Of the ones that didn't break, they pulled the threads out of the block.

    You are taking it apart and having a look but I'm going to guess the threads in your block pulled out.
    1997 R1100RT (Restored Basket Case) , 1981 KZ 440 LTD (Restored Basket Case, my baby, fast, fun)
    3xR90/6, two just sold, one for a sidecar. 1983 K100RS (Cafe now)
    Very Rough R80RT. 1987 K1100RS (freaking hooped I think)

  4. #4
    Registered User dmftoy1's Avatar
    Join Date
    Mar 2012
    Location
    Lexington, IL
    Posts
    660

    Ran into a nasty issue with the cylinder head mounting stud

    Not the end of the world, you're going to need to rent a jig to drill/tap/helicoil repair. Few places rent them, one that pops to mind is Jeff at northwoods airheads. I believe he rents you everything to repair properly. (I'm sure there are others). I do the tear down and ascertain what you need.

  5. #5
    Liaison 20774's Avatar
    Join Date
    Sep 2005
    Location
    San Antonio, TX
    Posts
    18,226
    Welcome to the forum! And sorry for this to happen...I can imagine what a sinking feeling that was. Looks like you were doing everything right. The upper end torque is typically 25 ft-lbs. I think some of the later sources recommend 29 ft-lbs, but the lower number is just fine.

    In the link in my signature line are a variety of resources. I have one for a /5 stud repair, a pictorial of the process. Check this out:

    https://picasaweb.google.com/1030509...OKW7sKaptKfQA#

    That should give you a good sense of what you need to do.

    If you think you need to get professional help, check out this link for Airhead-friendly shops...maybe there's one near you.

    http://micapeak.com/bmw/Airhead-Shops.html

    Also, you can find a wide range of Airhead related topics on Snowbum's page here:

    http://bmwmotorcycletech.info/techni...icles-list.htm

    Try to step back and assess the situation and take the course of action that will work for you. This can be easily solved!
    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
    Airmarshal-IL James.A's Avatar
    Join Date
    Sep 2013
    Location
    central Illinois
    Posts
    356
    I have done that repair my self on a 1988 R100RS. (see below) That particular bike had 2 pulled studs. After you have put the heli-coils in the stud holes you should drop the oil pan and be sure to flush out any particles that may have fallen in to the motor sump. It's a huge distraction on the way to a completed project, but not a disastrous end to a build. I know of at least one Airhead who does these free-hand, but a drill and tap guide is best. I have one for the later motors but not yours. Also, NO POWER TOOLS. You should do all the drilling and tapping with T-handles or similar manual devices.
    Last edited by James.A; 09-14-2015 at 01:16 PM. Reason: spelling
    1973 R75/5

  7. #7
    Thanks everyone for your feedback. I spent an hour this morning watching drill/tap/helicoil videos on youtube...

    I sent an email to Jeff at Northwoods Airheads to rent his cylinder stud thread repair jig. I will reply back to this thread with some progress photos.

  8. #8
    Sure enough the stud stripped the threads from the block:

    DSC01391.jpg

    Any recommendations for how I should clean the aluminum from the stud threads?

  9. #9
    Registered User dmftoy1's Avatar
    Join Date
    Mar 2012
    Location
    Lexington, IL
    Posts
    660
    I think you misinterpreted me as saying that timeserts are bad, I don't care whether he uses helicoil's, timeserts or anything else. My point is that drilling the cases without a proper jig is not a risk I'd take with my bike.

    Have a good one,
    Dave

  10. #10
    Registered User
    Join Date
    Oct 2011
    Location
    Ohio
    Posts
    1,244
    I feel it is also important to use a guide with the tap. The hole could be drilled perfectly straight but if the tap is crooked the stud will be crooked. You may be able to perform the installation but you will put undo stress on the stud and threaded hole if it is tapped crooked.
    Jeff
    93 K1100LT
    03 K1200GT gone but not forgotten
    14 Victory Crossroads

  11. #11
    Back in the saddle again mikegalbicka's Avatar
    Join Date
    Aug 2014
    Location
    Lakeland,FL
    Posts
    1,357
    Quote Originally Posted by jeffd View Post
    I feel it is also important to use a guide with the tap.
    I guess I have been very blessed during my 50 years of drilling and tapping hundreds of holes by hand only to have never messed one up. How did I ever get by without those fancy contraptions?

  12. #12
    Registered User a41capt's Avatar
    Join Date
    May 2015
    Location
    Camp Verde, AZ
    Posts
    16

    Yep!

    Quote Originally Posted by mikegalbicka View Post
    I guess I have been very blessed during my 50 years of drilling and tapping hundreds of holes by hand only to have never messed one up. How did I ever get by without those fancy contraptions?
    Right on pard.

    Using the tap guide to get you started ain't a bad idea for a newbie, especially since the tap included in the kit is a plug rather than starting tap, but the experienced folks shouldn't have an issue.

    As for drilling the old threaded hole, it's already there and square with what is needed. You're only reaming for diameter, and that's barely more than the old thread major diameter. Kinda hard to make the hole crooked unless it was already crooked before you started! We aren't filling and redrilling the case, just cleaning out the old thread pattern.

  13. #13
    Registered User
    Join Date
    Oct 2011
    Location
    Ohio
    Posts
    1,244
    It's the old oz of prevention / pound of cure thing. I like to minimize my risk when I can.
    93 K1100LT
    03 K1200GT gone but not forgotten
    14 Victory Crossroads

  14. #14
    Registered User dmftoy1's Avatar
    Join Date
    Mar 2012
    Location
    Lexington, IL
    Posts
    660
    Big difference between drilling and tapping by hand for a bolt, etc vs a stud that's going to stick out 10+ inches and upon which your valve train is going to rest being off by 1 degree by hand on a 1"long bolt isn't gonna effect much, but magnify the error by10. . .

Posting Permissions

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