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

  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
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    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
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  3. #3
    Registered User dieselyoda's Avatar
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    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
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    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
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    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
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    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
    Quote Originally Posted by danielb View Post
    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?
    Grab them lightly with pliers or your fingers and turn the stud. They will usualy screw right off.
    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://web.bigbend.net/~glaves/

  10. #10

    Recomend a new stud

    I would strongly suggest you invest in a new stud for that. It looks like the threads may be worn down at the aluminum collection spot

  11. #11
    Registered User a41capt's Avatar
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    Do Not Heli-Coil an Aluminum block or head!

    As the title of the reply says, stay clear of the Helicoil product for this repair.

    The correct product to use is called a time sert:

    http://www.timesert.com

    It is the preferred replacement because it is not a wire coil, but a solid tube threaded to fit your application. Helicoils pull out in most of these uses and you will end up tearing down again and replacing it with a time sert anyway. Spend the couple extra bucks and buy the insert kit for your job. It'll never pull loose or separate and will be worth the dough in the long run.

    Just did one myself on a stripped cylinder stud that some ham-fisted BMW dealer "technician" stripped at the 600 mile service on my R1200GSA...

  12. #12
    Registered User a41capt's Avatar
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    Forgot to mention...

    Helicoils are okay for cast steel and iron stripped spark plug holes, but I STILL use Timeserts for those applications because they are a superior option for critical strength repairs...

    50 years of motorcycle wrenchin' has taught me a thing or two about what works and what doesn't, and short of me tearing something down and putting it through my tig welder and mill to repair a stripped thread in a hole, the Timesert just works fast and easy.


    Quote Originally Posted by a41capt View Post
    As the title of the reply says, stay clear of the Helicoil product for this repair.

    The correct product to use is called a time sert:

    http://www.timesert.com

    It is the preferred replacement because it is not a wire coil, but a solid tube threaded to fit your application. Helicoils pull out in most of these uses and you will end up tearing down again and replacing it with a time sert anyway. Spend the couple extra bucks and buy the insert kit for your job. It'll never pull loose or separate and will be worth the dough in the long run.

    Just did one myself on a stripped cylinder stud that some ham-fisted BMW dealer "technician" stripped at the 600 mile service on my R1200GSA...

  13. #13
    I hear you on the timeserts, and my "research" on youtube shows timeserts being used over and over again. I am basing my repair on Jeff's page at Northwoods Airheads: http://www.northwoodsairheads.com/cyl-stud-jig.php

    Looks like his kit specifically uses a helicoil. Maybe this is not the right path... or I should use his kit for the jig and use a timesert kit instead?

    The cylinder head stud is thread size is M10X275 according to a replacement part I found online. What size timesert do I need? On amazon I found a set of M10x1.5x24.5mm timeserts for $22. With those timeserts and http://amzn.com/B001JK448O I should be good to go? Just to confirm, will M10x1.5x24.5mm match the threads on the cylinder stud?

    Thanks for the help and feedback. This is new territory for me. =)

  14. #14
    Registered User a41capt's Avatar
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    Helicoil

    I'm not an airhead guy so I don't know about the internal thread size, but that's a pretty jig that guy's got there!

    The Timesert kit should run about $70 and come with a drill and tap jig, the correct drill, the correct tap, and the insert and insertion tool.

    If the engine is still in the frame, you can certainly drill it in place without that jig, make sure that ALL openings into the block are sealed (I like clear packing tape) before you drill or tap. Remember Murphy and his most excellent law! Use WD40 as a cutting fluid with aluminum for drilling and tapping. Always, always, always back your tap up a minimum of 1/2 turn for every full turn going in to act as a chip breaker and keep from stripping your new threads as well!

    Be careful with blind holes. Measure the depth and mark your tap with a piece of tape at least one thread short of the bottom, and do it on the starting tap, the plug tap, and the bottoming tap. It'll save you a lot of heartache...

    Good luck, and welcome to the exciting world of motorcycle repair. Not many folks have the guts to tackle a job like this, but once you see how easy it is, you'll look forward to helping out the next guy and will be a hero in the process!

    Quote Originally Posted by danielb View Post
    I hear you on the timeserts, and my "research" on youtube shows timeserts being used over and over again. I am basing my repair on Jeff's page at Northwoods Airheads: http://www.northwoodsairheads.com/cyl-stud-jig.php

    Looks like his kit specifically uses a helicoil. Maybe this is not the right path... or I should use his kit for the jig and use a timesert kit instead?

    The cylinder head stud is thread size is M10X275 according to a replacement part I found online. What size timesert do I need? On amazon I found a set of M10x1.5x24.5mm timeserts for $22. With those timeserts and http://amzn.com/B001JK448O I should be good to go? Just to confirm, will M10x1.5x24.5mm match the threads on the cylinder stud?

    Thanks for the help and feedback. This is new territory for me. =)

  15. #15
    Registered User dmftoy1's Avatar
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    Quote Originally Posted by a41capt View Post


    If the engine is still in the frame, you can certainly drill it in place without that jig,
    It's your bike - but my .02 would be not to attempt to drill without a drill guide/jig. If you get it wrong you might be shopping for new engine cases.

    Good luck!

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