R25/3 Head Exhaust Threads

[Donovan]

Hello,

Moving onto the next potential issue with my bike. I was going to remove the head to paint it and I saw this.

It looks like the previous owner not only cross threaded the exhaust nut badly (by 2 threads it looks like) but they used some sort of silver sealant that is now very hard and brittle. I have seen this on a R75/5 once and it had ruined the threads on the heads when removing the nuts even when they were cut off.

I have talked with Uwe at S Meyer via email and he has a head that can be rebuilt.

Does this look like it would be repairable/salvageable or am I looking at a new head?

Right now it is sealed well ad the bike runs OK, but as soon as I mess with that nut there is gonna be trouble

Thanks,
Donovan

[Donovan]

[BenW]

You don't need a new head as the threads can be rebuilt. Dealers like Rabenbauer, Meyer, Stemler, or Ulis Motorradladen can do the job for around 100 Euros, much cheaper than getting a new or used head. Been there, done that, and it works fine.

Cheers
BenW

[Taz]

Hello Donovan.

My 2 cents...I would leave it for now and only lay hands on the nut once its inevitable...never touch a running system.

Basically this thread can be rebuilt from nothing (which would require some aluminum welding experience-I think at least some of the dealers here in Germany can do this as BenW already wrote but I am positive that there's metal worker around where you live who could this as well)...or you apply another remedy-there are several different concepts shown around the forum...

If this would be my machine's head I would leave it for now, and make sure I have a thread file available once the exhaust has to be removed in the end...then cleaning the threads carefully and see whether it's working...

Best regards, Taz

[skeewde]

Hello,

Moving onto the next potential issue with my bike. I was going to remove the head to paint it and I saw this.

It looks like the previous owner not only cross threaded the exhaust nut badly (by 2 threads it looks like) but they used some sort of silver sealant that is now very hard and brittle. I have seen this on a R75/5 once and it had ruined the threads on the heads when removing the nuts even when they were cut off.

I have talked with Uwe at S Meyer via email and he has a head that can be rebuilt.

Does this look like it would be repairable/salvageable or am I looking at a new head?

Right now it is sealed well ad the bike runs OK, but as soon as I mess with that nut there is gonna be trouble

Thanks,
Donovan

Hi Donovan,

if it's not salvageable i.e. can't be done up tight, then it can be cut off by a specialist and a complete new threaded piece welded on.

David

[skeewde]

Hi Donovan,

if it's not salvageable i.e. can't be done up tight, then it can be cut off by a specialist and a complete new threaded piece welded on.

David

Edit: note to self; write faster than the others in future!

[† Will]

Hi Donovan,
As BenW stated it's an common repair. Motorworks in England or Craig  at www.benchmarkworks.com/ in your country would be able to carry out the work required.

[BenW]

if it's not salvageable i.e. can't be done up tight, then it can be cut off by a specialist and a complete new threaded piece welded on.

Normally, cutting off the threads isn't necessary or advisable. The standard method of repair is to weld a layer of aluminum around the worn-out threads, then lathe the correct shape, cut the front, and tap a new thread.

Here's a picture of my head with threads repaired:


Cheers
BenW

[Kurt in S.A.]

If/when the nut has to come off, I would assess the issue at that time.  Depending on what you see, a metric thread file could be used to clean things up.

It's a common thing to do on the twins or any of these exhaust nuts to routinely remove the nut and renew the anti seize compound.  At least that's what you're supposed to do!  When I first got my /7, the Internet didn't exist  so when removing the nut, I galled the threads.  Note to self (and others)...if removing the nut, it begins to tighten up, stop turning the nut and use something to cut off the nut.  I suppose it's a more difficult proposition when the nut is captive on the header...it's not on the /7...exhaust nuts are cheap to replace.  Since I had ruined the threads, I had a local BMW mechanic aluminum weld on a new spigot.  It appears he machined down the old spigot, leaving a stub, and then fitted a new spigot and cutting new threads on the replacement.  I was so paranoid with that process, I never once again in 80K miles removed the nuts.  I recently did a complete top end overhaul on my /7 and without hesitation, cut the nuts off.  It was a good thing that I did.   

I like the recommendation of don't screw with a running motorcycle.  But there are definitely options other than replacing the head.

Kurt

[skeewde]

Normally, cutting off the threads isn't necessary or advisable. The standard method of repair is to weld a layer of aluminum around the worn-out threads, then lathe the correct shape, cut the front, and tap a new thread.

Here's a picture of my head with threads repaired:


Cheers
BenW

Okay, thanks for the correction. A long time ago I had something similar done to the mangled exhaust port of a Yamaha FS1E (yes, that long ago), and that was how they did it.

David