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R100GS exhaust nut

arptra

Member
hello all, does anyone know where I can get a thread chaser for head to clean up the threads for exhaust nut?
 
I used a metric thread file after I had to cut off an exhaust nut. Then, I used a good nut and some WD40, and that cleaned things up for me real well.
 
Any specialty tool house could order the metric die. I forgot what the pitch is...probably something like 1.5mm. As for diameter, 52mm sticks in my head.
 
McMaster Carr (check out on internet site) has just about everything known to man.

Also, any supply house that would be a supplier for machine shops, tool & die makers.

Be sure you know the thread pitch - in metric, it is the dimension from one thread profile to the next. In english, it is threads per inch.
 
If you don't have a metric thread file- or have not tried one- that would be a good first step. A die can damage the threads if not used correctly. I am not sure if the thread information below is correct for pitch or diameter - that needs to be measured before ordering.

Victor machinery (victornet.com) has a M52x1.5 die - RDM-52-1.5-F (http://www.victornet.com/subdepartments/Metric-HS-Round-Dies/1390.html). The price is $116.80. They also sell metric thread files: http://www.victornet.com/report/Thread-Files/1023.html

Personally, I would use a thread file. But if buying a die was needed, the die from S Meyer linked in this thread is preferred since it is made for an airhead and is less expensive. Good luck!
 
I have tried them all, I took the fin nut to a machine shop and they said it is 52x2mm and cant find anywhere. The two I have found are in Germany and about a month out. Will take it to Perry's side cars today and he should be able to fix it.
 
Thread chaser

I have tried them all, I took the fin nut to a machine shop and they said it is 52x2mm and cant find anywhere. The two I have found are in Germany and about a month out. Will take it to Perry's side cars today and he should be able to fix it.

If at all possible do not use a file or a regular die, try to find a thead chaser/repair die, it will not remove material like a thread die but will roll the thread back into shape.
 
With appropriate cuts across the threads of an exhaust nut, it can be used as a thread chaser in a pinch...maybe for light touch up.
 
McMaster does in fact have thread files. However, I think that they have the nomenclature incorrect.

They have listed metric thread files a "threads per millimeter" however it SHOULD be "mm dimension per thread to thread." This is most common error people make when referring to metric bolts and nuts.

For example: a 6 x 1.25 threads on a bolt means that the bolt diameter is 6mm and the thread is 1.25 mm from thread to thread. As the "pitch" dimension gets larger, the threads are more coarse.

Contrast that with the English way of thinking, which goes on a per-inch basis: for example a 1/4-20 means the bolt is 1/4" in diameter and has 20 threads per inch. Hence, the higher the thread number means the finer the threads. A 1/4-28 has a finer thread. being that there are more threads in the inch of distance.

Finally, a "thread" file does not designate diameter (as do taps and dies) because it must match the thread profile and is used like a file on the threads to clean them up.

Hope this helps.

Also, another alternative is to buy a small three cornered file. This would make the file a 60 degree angles which matches most thread profiles - whether metric or English. Just be careful not to file too much away. Take your time, and you can get the threads to clean up to almost like new.

Then, use copper-based anti-seize compound regularly.
 
Exhaust Threads

I have severely damaged threads on my right head on a 1977 R75/7.

I talked to Max BMW and they said that this is a common problem and that their in-house machine shop routinely welds and recuts the threads. So I took it to them yesterday. They thought that it would take a couple of hours to fix. We will see.
 
OK, I'm worried now...

I have two airheads and have never had to remove the exhaust nuts yet but this thread and others like it have me concerned that I should do so as a preventative step. I know the RS nuts have not been touche in at least four years and the G/S is new to me as of last year but with rusty pipes and collector box I feel quite sure they have not been touched in a very long time either. :nono I have the required tool.

So what's the best way to go about it to not end up with damaged threads?

- heat the nut up really well before attempting to move it?
- soak the threads as well as possible with penetrating oil for a day or two first? Tough to do this properly on a horizontal nut...
- how hard should you have to torque on the nut before it spins off?

Just looking for some advice but will probably just use common sense and feel when it comes down to it of course. I have lots of anti seize and should probably use some of it on these nuts sooner than later! :brow
 
On my Topend thread, I knew that I needed to just cut them off from the git-go...they had not been off in over 20 years and the anti-seize was gone. Good choice on my part.

If I wanted to take a shot at it, here's what I'd do:

- use the best penetrant you have...Kroil or the 50-50 mix of acetone and ATF
- heat the fins some and as it cools, introduce the penetrant...hopefully the cooling will draw it deep inside
- do this once or twice a day for at least a week
- time is your best friend here
- try to turn the exhaust nut off...get it to move maybe even just a little bit...
- then I'd try another 2-3 days of penetrant...the movement has opened up new paths for the liquid
- when finally ready, try turning the nut off
- you've heard the drill...if it moves some and then stops moving again, then you're at the point where thread damage maybe have started and time to cut the nuts off
 
Just looking for some advice but will probably just use common sense and feel when it comes down to it of course. I have lots of anti seize and should probably use some of it on these nuts sooner than later! :brow

The best advice and common sense is that the nuts are far cheaper to replace than restoring the threads. So, give it a try and if the nut don't want to budge, then I'd cut them off. I used a Dremel with two or three cutting wheels. I cut down at the top and bottom. Keep in mind you can't cut 100% through the nut due to the threads, so be careful not to go too far. I then used a flat crowbar with a 90 degree bend and twisted them apart.
 
Thanks for the advice guys. While I agree it would be cheaper to replace than to repair since that would involve a machine shop these nuts are not exactly cheap either. $32 each at Max BMW. If both bikes got new nuts that is $128 plus tax plus shipping I'd like to avoid paying if not necessary.

I'm going to try my best to get them off even if it takes a while. :D
 
Thanks for the advice guys. While I agree it would be cheaper to replace than to repair since that would involve a machine shop these nuts are not exactly cheap either. $32 each at Max BMW. If both bikes got new nuts that is $128 plus tax plus shipping I'd like to avoid paying if not necessary.

I'm going to try my best to get them off even if it takes a while. :D

If the previous owner put anti-seize on the nuts, they should come off without damage. Without anti-seize the nuts will gall and the threads will be damaged when trying to remove them. The likely hood damage occurs during removal is >90% w/out anti-seize . Try motobins (www.motobins.com) for new exhaust nuts. Cut the old off with a dremel - recognizing to not cut all the way through the nut before prying apart. Good luck!
 
Should I buy extra finned nuts before starting this procedure?

I didn't start this thread, but I am intrigued as I have kept up reading through it.

If one is planning to try to remove the exhaust nuts (mine is an R100/7, 1978) should one buy the exhaust nuts beforehand just to have them in case you need to cut off the old ones?

And if so, where is the best (least expensive, but not getting "look-alike" junk) place to purchase them?

Thanks ahead of time!
 
The old airhead that clean the threads on mine said if you break the nut loose and if it doesn't spin by hand then cut it off and use new nuts. Mine wasn't that hard to remove but I has to use the wrench and the threads off of the nut ended up in the threads of my head.
 
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