Exhaust options '74 850

I noticed a small hairline crack in the bend in the header just beyond the exhaust nut on the left side. I saw it a few days ago.

Took it for a 20 mile ride today and just as I was getting to my destination, I noticed a sound like leaking an exhaust leak. I get off the bike and noticed that when I put the kickstand down, the left pipe moved quite a bit. I thought the clamp between the pipe and the peashooter was loose. I soon discover the crack has worsened and it is now about 20 percent around the pipe. I bail wired it up as best as I could as a precaution against it breaking loose and dropping. I make the 20 mile trek home, taking it easy, and the sound is getting worse. When I parked it, it is about 85% broken around. I also have a peashooter that is breaking around the reverse cone.

Is it possible to effectively fix the header - weld it?

If not repairable, what are my options for a replacement exhaust and what have been the experiences with them?

I currently have a balanced pipe config(original) on the bike. It is not necessary to stay with that config and what are the pros and cons to that?
Commando Specialties has a set of headers and peashooters for $365 including shipping. Not a balanced pipe setup and they are listed as 750/850.

Any opinions and facts are welcome. Here is a pic of the cracked pipe.

Aha, the old cracking-around-the-balance-pipe problem !

A good aircraft welder could probably weld that up with stainless mig, and not make it look like a dogs breakfast. Would have been easier if the the crack was shorter though - probably now cost similar to new pipe(s). (And might re-occur).

Supposedly the balance pipe was mostly for noise control (trim a dB or 2), doesn't make much difference to the performance.

Interested to hear what you go with, how they perform and sound, I have old balanced pipes that probably don't have much life left, when I get it back on the road...

Rohan said:

Aha, the old cracking-around-the-balance-pipe problem !

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+1 on that. Mine broke exactly there in 1997. I kept the pipes and finally welded it but never had the heart to put it back on. Bought a whole new system from British Cycle Supply but no balance pipe anymore.

braze for a quick fix .

find a pipe bender with a Mandrel Bender and get a pair of S S 1 7/8 dia. high pipes , theres some stainless hot dog glass pack mufflers available ( Auto resonators ) .

Norvil pipes fit closer , if you whack the side stand bracket off , with a disc grinder .

Not reaally worth haveing a balance pipe on it . Plenty of Std ( ish :shock: ) headers available . Id check make for fit / durability / finish before purchase .Maybe Stainless ones ? .

In the 1980's the exhaust cracked on my 73' Roadster just like this. I welded it up In Situ with an acetylene torch and a coat hanger for filler. It went many more miles and never broke again. A quick fix that had me back on the road in short order.

I imagine these days will all the little mig welders laying all over the place it could be done very much more quickly.

BSA/Triumph used balance pipes for years, [even the triples were essentially 3-1-2] but Norton didn`t like the look, only went to them after NVT merger when showed research of how they worked, both for emissions [noise/gasses] & tuning..
For a laugh, see how Yamaha did theirs on the TX750, a hot spot/blind spot...

A self overheating cylinderhead , in fact .

Matt Spencer said:

A self overheating cylinderhead , in fact .

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Upon WHAT do you base that claim?

My 850 has a crack in virtually the exact same spot, although it's much smaller right now then what you have pictured. The main problem that I have is a backfiring issue due to the crack about 1/4" long. If it gets much worse I am going to go with headers without the balanced pipe, to me it makes the bike look better. If you find a good price on a pair of pipes please feel free to share with us.

beng said:

In the 1980's the exhaust cracked on my 73' Roadster just like this. I welded it up In Situ with an acetylene torch and a coat hanger for filler. It went many more miles and never broke again. A quick fix that had me back on the road in short order.

I imagine these days will all the little mig welders laying all over the place it could be done very much more quickly.

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Had to do a field repair a few weeks ago... the pipe was flapping after a high speed run. No TIG available, but a squirt gun with .023" wire did it up nicely. I REMOVED it first, didn't care to spatter or ignite the bike.

Yeah (TZ 750),based on what ? Mine ran great on the hottest days never overheating.Styling another story. My MK 111 has 750 pipes as a solution to the typical/eventual cross-over area cracking occurances. Sounds better too,more distinct-defined exhaust pulses.

Nice field repair Concours! Impressive.

I was lucky when I first built my 850 in a Wideline Featherbed frame, my local exhaust shop had a old Mandle pipe bender and Ian the owner was happy to build my exhaust pipes, he said at the time its been awhile sinse hes done a bike exhaust, I told him how I wanted them tucked as close to the frame as posiable, he did every bend by sight, it was a pleasure for me to be there watching him make them, with in a 1/2 hour he had the pipes bended right and sitting on the bike perfectly, he charged me $20 to make them and I was also lucky next door to his shop was a new chromers shop and a few days later I had my new exhaust system, I am still running these header pipe after 32 years on the bike and over 120,000 miles, they are getting a bit thin in places and one header has had a small hole brazed up but that was over 10 years ago, if I needed new pipes for it I would go back down this road and find someone with a mandle pipe bender.

Ashley

Snorton74 said:

Nice field repair Concours! Impressive.

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Thanks, 35 years of metal trade bliss, lol My bud and I joke.. "don't tell anyone I can weld, I don't want to do it anymore" lol

Torontonian said:

Yeah (TZ 750),based on what ? Mine ran great on the hottest days never overheating.Styling another story. My MK 111 has 750 pipes as a solution to the typical/eventual cross-over area cracking occurances. Sounds better too,more distinct-defined exhaust pulses.

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What about the 750 type NON crossover pipes v.s. crossover pipes as far as resistance to rocking/tearing up the port threads? Any opinions on that topic?

Get rid of the crossover pipes and you will never have anymore problems :roll:

Ashley

I can't see it making any significant difference to rocking or hurting the preciou$ exhaust threads. The exhaust nuts should be so goddamn tight it's not a factor. Other threads talk about this , anti-sieze or copper silicone ,proper ex. wrench tool it super tight then drive till hot ,then,tighten again with all your strength. Wires and lock ring arrangements only fool you as the loosened nut chatters out the preciou$ threads un-noticed. Vibration the real concern here as the cross-over pipe is fixed whereas the separate exhausts are free to bounce about on their own, independantly. But anything can crack from fatigue if not set up well....

Decemberist said:

My 850 has a crack in virtually the exact same spot, although it's much smaller right now then what you have pictured. The main problem that I have is a backfiring issue due to the crack about 1/4" long. If it gets much worse I am going to go with headers without the balanced pipe, to me it makes the bike look better. If you find a good price on a pair of pipes please feel free to share with us.

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That crack was much smaller that same morning. The reason I know that is that we have a group that meets for breakfast on Sun mornings and I pointed it out to one of the guys thinking that it may have been causing the pipe to blue. I rode it later that day and that is when it let go. Keep a close eye on it.

I bought and received the set of pipes and peashooters in the link below. They came in yesterday. I just sent out my head to get the threads repaired so I have a few weeks before it all goes back together. While I am waiting, I am replacing front pads, rear shoes and some other odds and ends and giving her a good cleaning. I may even attempt the rear ISO's.

http://www.commandospecialties.com/Prod ... &ProdID=20

concours said:

Matt Spencer said:

A self overheating cylinderhead , in fact .

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Upon WHAT do you base that claim?

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Just seeing the picture , I wonder if the new 961 designer owned one ? would explain a lot , wouldnt it .

The TX750 by Yamaha
Was smooth and slick like a bananaha
Counterweights revolved hard
On chain by the yard,
And oil leaked hither and yonaha.


Now , we are sorry . but seeing you asked .

Aluminum is fairly conductive . That silly thing across the front of the cylinderhead , not only conducts Exhaust Heat into the Front of the cylinder haed .
IT BLOCKS the Cooling Air FROM the front of the Cyl Head .
The oil Cooler positioned there does something like the same .

I believe the Japs read M C M , particularly the bit describeing ' The Closer the Balance Pipe is to the Cylinder Head , the more the low speed tourque
is improved . Describeing ' the latest advent ' in exhausts , I think by Dunstall . Soon copied across the board . IF NOT TAKEN QUITE SO LITERALLY .

Folklore has it the Japs sent out the top brass to Australia to watch the TX750 unveiling at production class racing in Sydney. The 3 bikes entered all had overheated oil problems. nuf said.

XS650 had a nice look and went well,but somehow the 500 and 750 did not fly.

Cheers Rich