Peashooter cracked

MS850 · Sep 27, 2016

Hello, I have about a 1k miles on my peashooter, the left side cracked just ahead of the weld. Ive read a few threads about this, one was using silicone at the muffler- pipe joint and a loosely tightened clamp. They are Commando Specialties, Ive contacted them.
MK3 with no cross-over pipe, header pipe has the ring and half moon holding pipe in head, no gasket.

Rohan · Sep 27, 2016

I've contacted them. ""

What did they say ?

To me, that looks as though the tubing needs to be heavier gauge, if its going to crack like that with so few miles...

Fast Eddie · Sep 28, 2016

I'd say they were over polished... They took all of the weld material away, that was also not properly penetrated.

MS850 · Sep 28, 2016

Rohan said:
I've contacted them. ""

What did they say ?

To me, that looks as though the tubing needs to be heavier gauge, if its going to crack like that with so few miles...

waiting for a reply,

Rohan · Sep 28, 2016

Fast Eddie said:
I'd say they were over polished... They took all of the weld material away, that was also not properly penetrated.

Maybe.
It looks like it broke beside the weld though, (the bead of which still seems to be there)
which to me suggests the tubing doesn't have enough thickness to it to have adequate strength.

Does your exhaust pipe poke into the muffler for a good way ?
(not just a short distance, which would really stress that weld area and around it).

Also, do you have the rubber mounted plates to bolt the mufflers to ??
If the engine end bobbles around, and the mufflers can't flex at their end, something in the middle has to give....

Matchless · Sep 28, 2016

This has happened to me three times. My exhaust system was fitted properly, with no stress on any part when bolted up. The first time both sides cracked within a few miles of each other. These items were ten thousand miles old. The second time it only broke the right hand side. This time after less than a thousand miles.
Fed up with this I phoned Brituro in Birmingham & got them to make me a set of Peashooters with a 1.5mm (16G) inlet tube. They are usually 1.2mm, which after polishing for plating is even thinner.
The right hand one cracked through in a very short space of time. I repaired that by brazing in a 304 stainless tube (1.5mm) & as you are doing, not tightening the clamp fully to allow some movement. This was at the suggestion of a forum member, can't remember who, but to whom I am very grateful. Four thousand miles on that so far.

Martyn.

concours · Sep 28, 2016

Performing as designed, I'd say.

engineering-compromises-leading-exhaust-threads-stripped-t14363.html

concours · Sep 28, 2016

Fast Eddie said:
I'd say they were over polished... They took all of the weld material away, that was also not properly penetrated.

Crack is at the toe ofthe weld, bead reinforcement looks intact.

grandpaul · Sep 28, 2016

A friend of mine had a set of Viking$ and they cracked there repeatedly...

You ARE running the 2 rubber isolators on each muffler mount, correct?

MS850 · Sep 28, 2016

The pipe goes in past the weld point, and I do have the two rubber insulators. The rubber is intact but seems to be old, probably flexes more than new ones.

Onder · Sep 28, 2016

More flex is probably better. Hobot , if I remember correctly, doesnt torque the fastener at the
joint and he cuts a waist into the rubber bobbins.
At very low speed the engine moves around quite bit. The pipes really need flexibility at the
mounts.

ILLF8ED · Sep 28, 2016

MS850 said:
Hello, I have about a 1k miles on my peashooter, the left side cracked just ahead of the weld. Ive read a few threads about this, one was using silicone at the muffler- pipe joint and a loosely tightened clamp. They are Commando Specialties, Ive contacted them.
MK3 with no cross-over pipe, header pipe has the ring and half moon holding pipe in head, no gasket.

I've had a few break in the same place. Pucchio welding in San Jose did a pretty nice repair without much discoloration. When tightening the system the muffler clamp is the last. Exhaust ring at the head and the rubber buffers at the Z plates first.

kerinorton · Sep 28, 2016

That one of the problems with electric welding. It can cause crystallization of the metal near the weld. I suspect that is what has happened. That is why, when building strength into structures, welding is done along the "grain" and never across the "grain" . I think you may know what mean here.
Dereck

APRRSV · Sep 28, 2016

Out of curiosity, what determines the direction of the grain and how do you recognize it, not only on steel tubing, but any chunk of steel?

Ed

Rohan · Sep 28, 2016

We are getting more into pseudoscience here, rather than science.
But tubing is extruded, so the 'grain 'flows more along the tube - or along the extrusion, for other types.
Fully extruded seamless tubing is generally stronger than tubing which is bent over and welded.
I don't recall welding classes including woodworking lessons on grainflow though. !
And all steels are a (terribly complex) crystalline labyrinth in microstructured alloys, so its easy to make sweeping statements. Mild steel isn't generally really affected by welding, unless you seriously overcook it.

I'd think its more a matter here that the inlet tubing isn't strong enough to survive long, if its not heavily anchored or reinforced there from flexing. The oem peashooter mufflers were surprising heavy, there was a lot of steel concentrated around that inlet tube - which latter day versions don't quite fully replicate ?

kerinorton · Sep 29, 2016

The word grain here is used literally. It means longways as Rohan has suggested. Ie if you want to weld two longer lengths of steel together longways, you overlap them and weld longways along the join. You don't weld across. Trouble is, you have to weld across when dealing with mufflers like here, or as Rohan has suggested, you extrude them out of one piece. That also leads to metallurgic problems as well so you can win unless you have plenty of money, make things a lot heavier, or because you have to do it for your aeroplane.
I imagine boiler makers and expert welders can do anything, but most of us [ mechanics ] don't have the skills.

Dereck

BTW, there is nothing wrong with welded tubing. It has been used in the automotive exhaust field for years without problems. Seamless tubing is far too expensive. I got a pair of pipes for my 850 just recently and they look good, and are made from seam welded tubing.

Rohan · Sep 29, 2016

With the reports of various types of mufflers cracking at the inlet pipe, I'm wondering if maybe they require a second layer of tubing welded over the inlet tube, for additional strength. Before chroming, of course.

You'd also need to take care that the muffler clamp isn't squeezing them too hard to cause them to crack - so the fit onto the exhaust pipe would need to be fairly close (not too loose that it would require a lot of squeezing).

MS850 · Sep 29, 2016

Thanks for all the input, still haven't heard back from Commando Specialties. BTW I installed these to replace the old set that cracked also, it was the right side on the old muffler that cracked

MS850 · Sep 30, 2016

Duane from Commando Specialties contacted me, like always great customer PR. He's sending a new one.
Everyone I have dealt with selling Norton parts have been fantastic.

cjandme · Sep 30, 2016

MS850 said:
Duane from Commando Specialties contacted me, like always great customer PR. He's sending a new one.
Everyone I have dealt with selling Norton parts have been fantastic.

Well, that's because Norton owners & riders are a fantastic bunch, don't cha know :wink:

Peashooter cracked

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