Engineering compromises leading to exhaust threads stripped (2012)

[Torontonian]

Everyone approaches the problem differently.
Por Moi : Clean the port and threads and ex. pipes ends of carbon .
Reassemble the port/pipes area using plenty of :
Permatex Ultra Copper advanced formula Maximum temperature gasket maker.
Smear it all over all internal contact areas.
Tighten up using correct Norton exh. wrench and a stanchion tube / 5 lb. sledge hammer or long bar on the end of the tightening/ loosening tool.
Run til' hot.
Repeat tightening up process.
Go for a drive.
Tighten up a final time , hot.
Cool down , crack a beer , peel off any orange Permatex that squirted out on assembly .
5 Nortons later , never a problem doing this.
No retainer rings , no screws , no ugly springs.
Enjoy.

 

[BERT]

I bought my 850 new in 75. In 1981 I had to have the exhaust threads repaired. Why? Because of these things...

View attachment 83329

After the good advice from forum members, I cut those off and had success with repeated tightening after each ride until they wouldn't tighten any more. And removing the exhaust nuts for winter work was no problem. I will use new gaskets again and make sure the pipes are seated squarely in the jug before tightening anything.

 

[BERT]

Everyone approaches the problem differently.
Por Moi : Clean the port and threads and ex. pipes ends of carbon .
Reassemble the port/pipes area using plenty of :
Permatex Ultra Copper advanced formula Maximum temperature gasket maker.
Smear it all over all internal contact areas.
Tighten up using correct Norton exh. wrench and a stanchion tube / 5 lb. sledge hammer or long bar on the end of the tightening/ loosening tool.
Run til' hot.
Repeat tightening up process.
Go for a drive.
Tighten up a final time , hot.
Cool down , crack a beer , peel off any orange Permatex that squirted out on assembly .
5 Nortons later , never a problem doing this.
No retainer rings , no screws , no ugly springs.
Enjoy.

I like the part about cooling down,cracking a beer and peeling off an orange Permatex

 

[Mart UK]

Someone wise warned me to make sure any balancer pipes are loosened off before tightening the rose nut. My LH exhaust was blowing. I undid it, cleaned and copper-slipped the thread and tightened back up. It took half a dozen rides followed by tightening, for if to hold. Has been firm since for a couple of thousand miles.

I'd left the lock tab washer on. So, once satisfied it was staying tight, I bent the tabs back over and they both broke off .

 

[Torontonian]

Someone wise warned me to make sure any balancer pipes are loosened off before tightening the rose nut. My LH exhaust was blowing. I undid it, cleaned and copper-slipped the thread and tightened back up. It took half a dozen rides followed by tightening, for if to hold. Has been firm since for a couple of thousand miles.

I'd left the lock tab washer on. So, once satisfied it was staying tight, I bent the tabs back over and they both broke off .

Never use a lock tab washer.
Have a nice day.

 

[concours]

A visual aid for better understanding:

Take a surplus header pipe, clamp on a pea shooter muffler, then grab it by the exhaust port end, both hands touching like a golf club, and SHAKE IT AS FAST AND VIOLENTLY as you can.

 

[concours]

Now take the same pipe/muffler assembly, grab it at the exhaust port end with one hand, and use the other hand to grab it down near the upsweep bend as shown.
NOWWWWW shake it violently, and understand how the pipe/exhaust threads are far less stressed and likely to fail.

 

[MichaelB]

Best I can see is, the exhaust threads being a problem area, is the result of multiple engineering EVOLUTION compromises. In the beginning, the head was cast iron and the threaded attachments probably worked just fine. Then the thread (head) material changed to softer aluminum... and they probably still worked OK. Then the Commando with Isolastic engine mounting system introduced lots of motion. And the four foot long pipe with a muffler hung on the end was hard to move from one end, overstressing the threaded joint. Then, in '74, the crossover pipe was added, requiring a shorter nut to make room for the split keepers now mandated by the crossover. 25% less threads engaged, failing even faster than ever. Item 17 here: http://www.oldbritts.com/1973_g23.html
View attachment 46112
As much as I want to keep my bike original, the crossover pipes are being binned. The longer nuts to engage all the threads will be added, along with a better engineered mounting system, to be detailed later.

For those that want a more correct appearing rose for non Balanced 850's, the 73- 750 Rose is long thread big fin.

Motorcycle parts and spares for Norton motorbikes - Genuine Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Genuine Factory Spare Parts for Norton motorcycles built before 2002.

andover-norton.co.uk

 

[KiwiShane]

Nice bracket design
Questions
Whats the best way to get a seized header pipe thats stuck in a prized muffler without damaging anything ?

Do you think the type of head steady used has any influence in regards to exhaust rose nuts loosening ?

 

[concours]

If you're sacrificing the header, cut it off close, use a sawzall (reciprocating saw) to thin it out in three places. Grab it with vice grips, roll it in on itself.

No opinion on head steady, other than design goal is to all fore-aft and up-down movement with no side to side.

 

[KiwiShane]

If you're sacrificing the header, cut it off close, use a sawzall (reciprocating saw) to thin it out in three places. Grab it with vice grips, roll it in on itself.

No opinion on head steady, other than design goal is to all fore-aft and up-down movement with no side to side.

Its the header (timing side) I brazed up years ago thats stuck in the muffler....would like to possibly save the header as well ?
What do you think of this idea of Brookings to lock the rose nuts up against the head with a modified lock ring (tabs chopped off) to bite up against ?

 

[concours]

Its the header (timing side) I brazed up years ago thats stuck in the muffler....would like to possibly save the header as well ?
What do you think of this idea of Brookings to lock the rose nuts up against the head with a modified lock ring (tabs chopped off) to bite up against ?

The rose nuts need no locking mechansim, if you get them tight enough.
Any locking mechanism, including OEM rattle rings, will CONCEAL a loose nut, and the threads will be vibrated to hell BECAUSE of the locking ring.

Secure the muffler to something solid, HEAT the muffler joint, 400F, and twist/pull the header out (welding gloves)

 

[Bonzo]

I removed my pipes as it was blowing a little around the balance pipe - maybe one day when I have some extra funds, I'll go for a none hassle, none balanced 750 set

Out of interest what do you guys apply to the rose nut threads? I used Graphogen as recommended by Norman White, however I've found it runs and leaves a pissy coloured stain around the fins



Full marks for the Steve Maney thread repair, which is looking as good as the day it went in

 

[concours]

Out of interest what do you guys apply to the rose nut threads? I used Graphogen as recommended by Norman White, however I've found it runs and leaves a pissy coloured stain

Post #5.

 

[cash]

While rummaging through my junk box I found an original pair of bronze Domie rose nuts and out of curiosity I measured the thread OD and found they were 0.025" larger than than the bronze ones I had fitted some 25 years ago. I found the old Domie rose nuts were a nice fit in the ports and used them. So far they haven't moved and or required any nipping up.
I wonder if over the years the thread tolerance has been allowed to slip. Is this another reason why exhaust port threads are pulling out?

 

[concours]

While rummaging through my junk box I found an original pair of bronze Domie rose nuts and out of curiosity I measured the thread OD and found they were 0.025" larger than than the bronze ones I had fitted some 25 years ago. I found the old Domie rose nuts were a nice fit in the ports and used them. So far they haven't moved and or required any nipping up.
I wonder if over the years the thread tolerance has been allowed to slip. Is this another reason why exhaust port threads are pulling out?

Nothing would surprise me. Been in the metal trade my whole life.

Genuine Yamaha part pictured, old then new. Made thinner, and of the wrong material.