Do I need a new head?

[quixotic]

OK, I realize that after this bit of stupidity, I could use a new brain, but for the purposes of this thread, I'm actually referring to the bike.

I was going to take the finned nuts off to see if there was any corrosion.  In the back of my head, I knew that the manual said to loosen all of the exhaust system nuts and bolts.  But the nut on the right cylinder came off like butter, so I put that thought aside.  The left cylinder was a doozy, but it was coming, so I kept on reefing on it.  And the rest is history. [smiley=wall.gif]

I realize now that the left exhaust pipe still has some radius close to the cylinder, and that was why I had to reef on it.  

Anyhow, it's all back together now.  The left nut seems to be on there solidly, and there's no smoke or noise coming out from the junction.  I guess I just don't know how long that state of affairs will last.

But the whole episode puts me in mind of aftermarket exhaust systems.  Are there any bolt on types?  I recall seeing just a day or so ago a different arrangement for the nut: something clamped around the cylinder head exhaust protrusion, and then a finned nut bolted to it.  Any ideas?  

[Bob_Roller]

Not uncommon to have this happen to an exhaust nut .

The usual advice, is if the nut loosens then tightens up again, cut the nut off .

Well, you can leave it like it is and see what happens in the future .

The threads can be repaired, I had it done to both heads on my '81 R65, wasn't too costly at the time, don't know what the going rate is now for the repair .

I vaguely remember a member here using the clamp on type repair, instead of having the threads repaired .

Can't remember, if anything needed to be done to the outlet port to install this or not .

[Tony Smith]

Dear as poison, but they look the goods:-
http://www.sternmutterersatz.de/BMW-V2-Airhead-Exhaust-Clamp-Details.html

I would consider using them if your current arrangements fail. A long time ago, when I owned a share in a much bigger lathe, I repaired the heads from my R100 having done pretty much what you have done - only better, I totally ruined the threads.
 
First you make a  "L" shaped fixture that the head can be bolted to and which in turn can be bolted to the faceplate of your lathe. While you are busy making this fixture, send the head out to a person specializing in non-ferrous welding and have them grind off the thread and then build up a nice substantial amount of metal where the threads used to be.
 
Then, bolt the head to your fixture and then bolt the fixture to your lathe's faceplate. Spend 30 to 45 minutes carefully setting thing up so that the exhaust hole is exactly centered. Turn off excess metal and bring the diameter down to the correct size to cut a thread then get out your best thread cutting tip and set your lathe up to cut a 1.5mm pitch thread, cut thread with multiple passes, use a brand new exhaust nut to check. Remove head from fixture, coat thread liberally with fine valve grinding paste and then run nut on and off about 10 times.

Clean very carefully.

Ok, unless you are lucky enough to find a machinist who already has a fixture fro an R65 head made up (and who has already fully recovered his time in making same), your costs are going to look like this.
 
Welder -
to grind off remaining thread and build up weld for thread to be cut into ~ $70 ~ $100.
 
Machinist -
to make fixture to hold head - $200 ~ $350
set up in lathe turn off excess metal and cut thread - $70 ~ $100
clean up thread and provide running clearance by lapping with grinding paste, clean head - $50 ~ $70

or.
 
Buy used head from eBay with good thread but worn guides/valves - approx $150

Buy complete kit of new intervalve valves, new guides, springs and collets (currently on special from motobins at around $160 for set for two heads)
 
Take your remaining good head and the one you bought to auto engineers and have them fit new guides, collets, springs and valves, correct valve seat reconditioning, vapour blast heads ~$350

The costs work out similar, but the second method gets you reconditioned heads.

I do feel sorry for you as I have done EXACTLY the same thing myself. The only bit of luck on my part was that I had access to both the machine tools to fix them and access to people to teach me how.  I would offer to fix yours for you, but alas the lathe I own now is too much of a toy to even attempt that job.

The mantra is, if the nut tightens up, cut it off - nuts costs a fraction of a head repair.

[quixotic]

Dear as poison, but they look the goods:-
http://www.sternmutterersatz.de/BMW-V2-Airhead-Exhaust-Clamp-Details.html

Thanks.  That's precisely the link I need.  I think I'll probably order a set and keep them on hand, just in case.

The mantra is, if the nut tightens up, cut it off - nuts costs a fraction of a head repair.

The other mantra -- which I now know by heart -- is to read the Haynes manual carefully...even if I'm sure that I already know what it says.  

[Bob_Roller]

One thing that has not been mentioned, is the need to use anti-seize compound on the threads .