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85' 80RT exhaust flange damage  

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bradley martin
(@dartnmartn)
Active Member Expired Membership
Currently working on a 1985 BMW 80RT. 
 
Took the exhaust system off.  I have one of the BMW exhaust flange wrenches and things came apart sorta OK.....  The right-side flange spun right off without much forcing.  The LEFT flange put up a little fight.  I put some heat on it and eventually got it removed.
 
Reassembly time!  The right flange spins right on by hand.  The left....??  I started it very carefully by hand.  Started threading it on by hand for a couple spins...it started to feel a bit tight, so I put the wrench on it.  I worked the wrench back and forth lightly, just to try and clear any foreign material that may be giving me heartache.  Obviously just a bit more tightening than loosening as I worked it on.  Then.... BAM!  It was LOCKED.  I'm talking jammed up SOLID!  Heat it up and bang it off with a rubber mallet solid.  And not just to get it loose.  It fought me all the way till it fell off.
 
So..  now I have a trashed flange nut but WAY WORSE....  The threads on the head are buggered pretty bad too!!
 
Is there a DIE (as in tap and die) available to chase these threads?
What size is it?  Diameter and thread pitch.
Is there one available amongst the airheads that I could borrow??  I see a 56mmx2.0 die on ebay for $85 bucks...OUCH! (approx size don't know if this is the right diameter and pitch)
 
Any suggestions on what to do/ how to do?
 
I'm not in a huge hurry, but I am open for any expert help!
 
Thanks
 
Brad Martin
Quote
Posted : 11/16/2020 12:59
Brian Swanick
(@thundermotive)
Estimable Member Expired Membership

There are machine shops that will saw the old flange off and weld on a new one. I'm not sure about the cost. 

This is a tool I use in my actual job that I've had very good results with. Never tried it in that application.

https://www.mcmaster.com/thread-chasers/side-grip-external-screw-pipe-and-conduit-thread-repairing-tools-7/

ReplyQuote
Posted : 11/16/2020 15:58
Richard Whatley
(@wobbly)
Member Moderator

Never ever assemble the exhaust flange onto the cyl head without a fresh coating of high temperature "never-seize". The alloy in the head and the alloy of the flange are just similar enough that they have a very high affinity for each other. "Seizing" and "galling" are simply terms that describe the transfer of metal from one part to the other, much akin to welding... and just as permanent.

The only way to separate the 2 parts now is to slowly cut away the finned exhaust nut with a Dremel tool. The sections that have not become part of the cyl head will fall right off.

You can buy a die to clean the threads after-the fact, but the one-time way is called a "thread file". Either way you need to exactly match the tool to the threads (in this case metric) to get good results. 

The numerous "never-seize" products work by breaking the "similar metal" kinship bond by laying down a dis-similar metal in the threaded joint. Threads by their nature are very close-fitting, and so the compound MUST be re-applied each time the part is being re-installed. This warning is part of every BMW manual and every Chris Harris Airhead repair video. 

I believe this is the product Chris Harris uses.   I prefer the nuclear grade product with nickle    . 

The product is also useful on spark plug threads and several other places on an Airhead. These include exposed fasteners that might need to be loosened on the side of the road for emergency repair.

Hope this helps.

 

https://www.youtube.com/watch?v=ZRXKC9Yxfug

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 11/17/2020 12:09
Joe Hall
(@joe-hall)
Active Member Expired Membership

@wobbly

I recall the warnings about exhaust flange thread seizing from days of old. I recently bought my first Airhead since about 15 years ago, a 1995 with 25,000 miles. One of the first things I did was gently break the nuts loose and screw them off, and slather antiseize on both the nuts and head flanges. My practice is, about once per year, back the nuts off about 1/2 turn, then retighten. That, along with the generous coat of anti seize, will hopefully keep them from ever seizing.      

ReplyQuote
Posted : 11/17/2020 18:20
James Strickland
(@8053)
Honorable Member Expired Membership

There should be a die available somewhere to match this thread pitch. I do not own one myself. You might try contacting one of our advertisers to check in to a repair, or to find out what the thread pitch is. If I ever had that problem with a bike I owned, I would just pony up the dough to get the correct tool. That way, I would always have it, and might loan it to other members. There was some talk recently about compiling a tool loan list.  

https://www.airheads.org/community/?wpfs=tool+loan&wpfin=entire-posts&wpfd=0&wpfob=relevancy&wpfo=desc

This post was modified 2 weeks ago by James Strickland
ReplyQuote
Posted : 11/21/2020 09:12
James Strickland
(@8053)
Honorable Member Expired Membership

O.K., I went outside and cleaned out the gutters on my house and thought this over for a bit. I decided to bump around other Airhead web sites and found the following thread on Adventure rider. it is from 2013.

https://advrider.com/f/threads/stripped-exhaust-threads.875498/

Among other info in the thread, the thread pitch is described as 52x2, in mm of course. If you decide to purchase or borrow a die for the purpose of chasing the threads, I'd put the odds at 50/50 for a successful result depending on how bad the original threads are damaged.

 

This post was modified 2 weeks ago by James Strickland
ReplyQuote
Posted : 11/21/2020 12:29
Richard Whatley
(@wobbly)
Member Moderator

The correct thread designation is: M55x2

Mcmaster-Carr and other tooling sources max out around 35mm. However, there is a seller on Ebay with one for $70.

https://www.ebay.com/itm/114303414587

[color=blue]Don't hide 'em, Ride 'em !!
#15150[/color]

ReplyQuote
Posted : 11/22/2020 04:43
8166
 8166
(@8166)
Honorable Member Expired Membership

A couple of thoughts.

I have the correct die for the exhaust threads, but because of the finning on the head, it can't be screwed all the way on to the threads. If you were to find a 2mm thread file and use it carefully, you might be able to salvage the thread.

Randy Long recently repaired an exhaust thread on a head I sent back to him to have an additional spark plug hole added. Marvelous job; can't even tell it was repaired. He had me send him an exhaust nut with the head so he could make sure the thread was cut properly. A search for Long's Mechanical should turn up his contact info, and he's in Pennsylvania. He's not much of a computer guy, so he's best reached via phone call.

ReplyQuote
Posted : 11/22/2020 11:59
Leif Dickinson
(@13749)
New Member Expired Membership

I bought a die on Ebay out of Belarus, $40. Russian made, luckily only cutting aluminum. Welded it onto an old Snap-on socket and saved the threads on my daughter's R80. As long as the threads aren't boogered too bad the die will do fine.

ReplyQuote
Posted : 11/26/2020 05:47

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