Exhaust port repair

I prefer to ensure the roses are tight.
With lock wire, the rose will not come completely undone, but could allow the rose to be slightly loose, fretting away at the threads.
 
If the lock wire is applied correctly there is no way it can loosen.
Tighten the rose with the engine hot and running. Locate a point tangentially to a rose fin, then apply the lock wire through a hole in the rose fin. Twist the wire from your anchor point or slightly close to the rose, as it twists it will shorten. Pass the wire through the anchor point and twist from about 20mm beyond. As the wire twists it will put tension on the rose ensuring it stays tight. Finally snip the ends at the final twist and bend the twist in half to leave a smooth end
 
Better than just static lock wiring. Live loaded after tightening. Allows you to remove and refit without using any lockwire or lockwire pliers. Never had any come loose.
 
That would work but I'd do it more neatly, maybe replace the wire loops with "S" hooks bent up from 3mm stainless steel wire hooked between the spring and hole in rose fin
 
As to the welded in repair. The new threaded section should not be straight through, but have a seat on the bottom. The pipe would but up against the insert and not the head itself. This would stop the pressure of the tightened exhaust nut from pushing the insert out of the head.
Not an original idea to me, but read about it on this site.
 
The problem is the design. Hundreds if not thousands have failed because the nut loosens and then the threads pound out. Redesign so the pipe slips in (add sleeve) and is held with a spring and the problem is solved forever. Screw the nut in tight till it bottoms out. Use high temp silicone bronze brazing rod on the sleeve and the spring catch. Seal threads and sleeve with high temp RTV and retighten nut when hot. Then forget about it.

Exhaust port repair


BTW if the threads are just starting to fail you can expand the nut by machining plugs in .010" increments and press them through the Ex nut until the threads are a good fit again.
 
robs ss said:
This is probably a bit like an oil thread but...
I never use any compound on the threads - my rationale being if the lube helps it tighten, it'll also help it loosen.
I have a two foot length of pipe that fits nicely over the rose spanner. For final tightening I ensure the head is good and warm then apply tightening pressure with the engine running.
Vibes plus heat seems to work - they stay tight.
I also check for looseness (hot or cold) every month or so, just in case.

I never lube spark plugs either - same reason
Cheers
Click to expand...
Very good advice .
 
I believe that if the downpipes should be braced to the engine around the front ISO. This would stop flexing at the head.
With the standard set up it is the equivalent of flexing the downpipe up and down, constantly crushing the gasket thus loosening the fit. The flexing will also be applying an up and down load on the rose and head thread.
 
Andy Higham said:
I believe that if the downpipes should be braced to the engine around the front ISO. This would stop flexing at the head.
With the standard set up it is the equivalent of flexing the downpipe up and down, constantly crushing the gasket thus loosening the fit. The flexing will also be applying an up and down load on the rose and head thread.
Click to expand...
Correct solution. There is also an exhaust vibration mode causing the ring nut to unscrew. I fitted a simple attachment to tie the downpipe to the front ISO engine mount (on the engine side of the mount NOT the frame side). Problem solved.
 
I just so happen to have received a head back from Jim Comstock today. He installed bronze exhaust port inserts, installed 3/8-16 helicoils for CNW/ARP head studs, and cleaned and peened the head. Of particular interest to this thread, my head originally had welded in aluminum inserts (from the PO). The welds were actually quite decent and the threads were still fine, but it was destined to crack and cause ugly damage to the head at some point.
I was concerned that there wouldn't be enough meat left for Jim to install his inserts, but he did a fantastic job. And his vapor blast and ceramic ball peening really cleaned up the head.
Jim's services are very reasonably priced. I sent my head on Feb 10th and got it back March 12. In my book that's great service.
"Baz", if I were you, I'd send your heads to Jim.
I'd like to echo the comment of "Deets55"'. I had the pleasure of meeting and chatting with Jim at the INOA rally in Quincy last year. Jim is very personable and has tons of great stories. I couldn't be happier with Jim's work. The best way of contacting Jim right now is via his juno.com email.

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DennisMo said:
Can I ask you advice on how to avoid having exhaust thread problems? On my 850, I put some copper never-seize on the threads and tighten then use a maul to whack it hard. Then retighten a month or two later.
Last summer I had a nut come loose while riding. Luckily I heard a strange exhaust note, stopped, noticed the nut almost unscrewed to falling off. I spun it back hand tighten with my gloves on and rode home. Then tightened
Thanks
Dennis
Click to expand...
I've heard that high temperature silicone sealer (copper I believe). NOT anti seize lubricant. will decrease the possibility of them coming loose.
 

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