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.

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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:

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

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.

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.

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/103050...hreadRepair2010?authkey=Gv1sRgCOKW7sKaptKfQA#

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/technical-articles-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!

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.

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.

Sure enough the stud stripped the threads from the block:



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

danielb said:

Sure enough the stud stripped the threads from the block:

View attachment 51734

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

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Grab them lightly with pliers or your fingers and turn the stud. They will usualy screw right off.

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

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...

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.

a41capt said:

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...

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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. =)

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!

danielb said:

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. =)

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a41capt said:

If the engine is still in the frame, you can certainly drill it in place without that jig,

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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!

Drilling and tapping

The Helicoil guide that he is referring to is for a different system and is probably for the wrong size drill bit. The Timesert system comes with a tap guide that can be used for the drill, but the drill is sized so that it follows the original hole closely.

Here is a link to show you how it's done since I've never taken any pictures of my own work:

http://www.klr650.marknet.us/timesert.html

It really is very simple and unless you're a complete idiot, a skill that can be performed by anyone with a couple hand tools, a drill motor (optional), and the balls to just go to work.

And that's 2 cents from a guy who has actually used both the Helicoil and Timesert systems.

dmftoy1 said:

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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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

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

jeffd said:

I feel it is also important to use a guide with the tap.

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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?

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. . .