pipe broke

commando6868 · Aug 13, 2014

68 Commando, new pipe with less than 100 miles on it, broke off right at the nut, at the head. Has this happened to anyone else? New, UK made pipes, my supplier is looking into getting another one for me.

MF

Hobot · Aug 13, 2014

Only those that ain't leaned the errors in the manual on header install and completely sips over the proper thermal compensation similar to primary chain tension, so no very rare to ever hear such a failure...

Can ya see me snickering. Its too damn common but rather rare not to get years out before cracking. Also rare to fracture that close to the ring nut. 3 sets I've seen give way at first sharpest down bend. Exhaust must be free to oscillate with power unit so after my 1st 2 set of pipes broke I waist the Lords mounts and leave the muffler junction an easy sliding fit so no tools to pull apart or push back in. Other 3rd set was my '71 buddy's, as usually he welds em up or replaces em before i get to see em.

mikegray660 · Aug 13, 2014

make sure you have good isolation rubber things (new and not old hardened) on the mufflers and they are not hitting up against the frame (some rubbers have extra long threaded sections and will hit the swing arm/frame) and that your head steady is properly adjusted

Torontonian · Aug 13, 2014

If driving , pull over to farm or shop where crack-off occurred and use binder twine to twist up to get home or preferably weld up the P.O.S. on site to get home. If at home just order in new pipes. Like Hobot said they don't normally crack there so perhaps isolastics jammed up or bad rubbers ?

edward · Aug 13, 2014

hobot said:
Exhaust must be free to oscillate with power unit so after my 1st 2 set of pipes broke I waist the Lords mounts and leave the muffler junction an easy sliding fit so no tools to pull apart or push back in.

Am I correct in assuming this means that the muffler clamps should NOT be fully tightened over the exhaust pipes? I've just tightened mine because I was concerned about air leaks in the exhaust system.

ed.lazda · Aug 14, 2014

Happened to me recently. Riding home from work, bike starts running a bit rough, OK if you keep the revs up. Get home and find one pipe broken through just before the bend.

Asked a similar question on a different forum, summary of responses: "They all do that, sir."

concours · Aug 14, 2014

Mike, my repair outlined here: engineering-compromises-leading-exhaust-threads-stripped-t14363.html?hilit=Exhaust

YMMV

commando6868 · Aug 14, 2014

Just to clarify, the pipes were installed correctly, the threads are not cross threaded, did not strip, rubber mounts are good, nothing is hitting the swingarm etc. I have installed pipes several times before and I have owned several Commandos, I have 2 now. I have been riding UK bikes since 1970, ( yeah, I am old!), and I never had a pipe break. I am waiting to see what Andover Norton has to say, they have all the photos.
I was less than 1 mile from home when the pipe split, so no problem limping home very slowly with the mechanics wire, everyone carries some of that, right?
I was riding home from the next town, Boxford. We were looking at a 73 Commando that belongs to one of the NENO members who passed away, recently and unexpectedly. His widow wanted to get an idea what the bike is worth so she can sell it. It runs, pipes and mufflers have rust on them and needs a battery. Whats that saying, "no good deed.........."

Hobot, WTF are you talking about!!?? :mrgreen:

MF

Hobot · Aug 14, 2014

WTF I'm talking about is it's luck of the draw on old or new parts integrity so no matter what some percentage will fail no fault of your own, but, sometimes can be compensated for by cleaverness or trial and error. Besides the main up/dn hopping at front by pistons and suspension bump action, on the road the whole power unit also moves fro & aft from loads lengthwise through the isolastics so unless pipes given some slack relief by more compliant Lord's mounts &or slipping joint into muffler, metal fatigue flexure is concentrated in the first 6" of the headers out of engine. How long can a header stand this, wtf knows. Due to this weak area affecting others out the blue a good number of builders have given up and made muffler mounts attach to the cradle, which process can't be found in the manual either. Regardless owning a Commando means someone's going lose some more money and time, trying for a vendor replacement they get to eat or spending it yourself, again.

commando6868 · Aug 14, 2014

concours said:
Mike, my repair outlined here: engineering-compromises-leading-exhaust-threads-stripped-t14363.html?hilit=Exhaust

YMMV

Good info, so far I haven't stripped any threads. It's still early tho.

MF

commando6868 · Aug 14, 2014

hobot said:
WTF I'm talking about is it's luck of the draw on old or new parts integrity so no matter what some percentage will fail no fault of your own, but, sometimes can be compensated for by cleaverness or trial and error. Besides the main up/dn hopping at front by pistons and suspension bump action, on the road the whole power unit also moves fro & aft from loads lengthwise through the isolastics so unless pipes given some slack relief by more compliant Lord's mounts &or slipping joint into muffler, metal fatigue flexure is concentrated in the first 6" of the headers out of engine. How long can a header stand this, wtf knows. Due to this weak area affecting others out the blue a good number of builders have given up and made muffler mounts attach to the cradle, which process can't be found in the manual either. Regardless owning a Commando means someone's going lose some more money and time, trying for a vendor replacement they get to eat or spending it yourself, again.

I don't know what Andover Norton will do on this, I will post the results. If I have to, I have someone who is a good welder close by.
Beautiful day to ride here in PRM.

MF

tricatcent · Aug 14, 2014

I often wonder how many of the pipes broke on brand new machines while they were still under warranty. It seems amazing that the system used works at all. I think somehow the factory must have had it worked out.

Nigel

JimC · Aug 14, 2014

I restored my Commando in 1999. New pipes. Don't remember the brand. One pipe split length wise for about 3 inches after about 2,000 miles. Got another set of a different brand from the same vendor. As a matter of fact, the new pipes have the MkIII collets. The vendor is a well known Norton parts supplier. The new pipes are still going great after some 20,000 miles. Lead me to believe there are some bad pipes out there. Same installation, same iso rubbers. As for welding cracks, you are creating a stress point at the weld and if someone can weld without burning the chrome, my hat's off to them.

Just hand tighten the rosebuds, tighten the muffler clamp, then tighten the isos. The isos should be straight and not in a strain. Lastly, get your Norton exhaust nut wrench and put a 3 foot cheater on it and tighten the beejeezs out of the rosebuds. Might do to have someone sit on the bike while you tighten the right side rosebud. I did safety wire mine, but I never had an exhaust nut loosen.

commando6868 · Aug 14, 2014

JimC said:
I restored my Commando in 1999. New pipes. Don't remember the brand. One pipe split length wise for about 3 inches after about 2,000 miles. Got another set of a different brand from the same vendor. As a matter of fact, the new pipes have the MkIII collets. The vendor is a well known Norton parts supplier. The new pipes are still going great after some 20,000 miles. Lead me to believe there are some bad pipes out there. Same installation, same iso rubbers. As for welding cracks, you are creating a stress point at the weld and if someone can weld without burning the chrome, my hat's off to them.

Just hand tighten the rosebuds, tighten the muffler clamp, then tighten the isos. The isos should be straight and not in a strain. Lastly, get your Norton exhaust nut wrench and put a 3 foot cheater on it and tighten the beejeezs out of the rosebuds. Might do to have someone sit on the bike while you tighten the right side rosebud. I did safety wire mine, but I never had an exhaust nut loosen.

Jim,
So welding is not a good option? The break is almost into the inside of the exhaust nut.
The factory pipes on my '75 had about 30,000 miles on them with no problem. I decided to get a set of Vikings, they now have 36,000 miles on them, neither set has loosened up.

MF

Hobot · Aug 14, 2014

Look this type event means you either assembled it wrong, by listed manual protocol or one of your own &or the item had a fault or all these at once. So let us know when ya find out which above or none the above applies. I guess most of ya don't know how long weld repair is expected to last > if not also backed up by a strap added too. The more sure of themselves on giving set advice and firm judgments concerning a Commando and its quality of parts, the more its publicly apparent they lack full scope of seasoned experiences to do so. My most expensive regret, expecting not buying a used mower instead of 1st Combat, was detailed pow wow with the Viking exhaust owner on fit, finish and gauge of tubing but waiting some years to use as Peel worn out too soon so deer downed Trixie got them, which required opening up to risky thinnest the nice bronze ring nuts and grinding down flange to risky thinness and finally putting a kink in the thick tubing because it clashed into point cover otherwise. I've met my match in keeping up with a Commando that's got so many conflicting issues surrounding it too.

Onder · Aug 14, 2014

At some point in the not too distant past somebody posted a picture of a bracket that went from
the cradle to a few inches up from the end of the exhaust pipe. This looked like it solved the
stress on the head end of the pipe.
So how did this idea work out?
Also airplanes use slip joints in their exhaust pipes. Stuff on recips cracks all the time. The
idea of not cinching the silencer to the pipe might not be a bad idea but then the silencer is
out there wiggling around on those sad little rubber biscuits.

Torontonian · Aug 14, 2014

Don't know how a slip joint works but do know CNW has developed a new system of small springs to replace the fragile little rubber donut mounts for the Mufflers. Expen$ive they be but may be a big aid to eliminate strain/allignment issues. Remember that way back when at the Factory each pipe was selected individually from the stockshelf to test fit and if not then take off and try another or go to the bloke who bends 'em up and have a chat. :roll:

Hobot · Aug 14, 2014

Its so very rare to crack up close to head likely ZDF will just replace it as your own experience verifies ya know what ya doing and what is very abnormal. The last part of Peel's 2-1-Dunstall mega used two springs but more stop gap for raw off road stuff. Next time out will make a 45' twist in a mount so rubber cushions not completely supporting the whole moving mass in pure shear loads.
Do not try to weld under the nut as for sure will not last long in that violent area and if lets go out of head it can blast swing pipe all the way to the ground and snag ya off if not scaring ya off by the sudden extreme noise.

milfordite · Aug 15, 2014

It happens. I was running original head pipes for an early fastback and they both cracked/broke near the head. Brazed from the factory. Pipes were installed correctly. You need to find a good welder! One of mine broke in New York and one in California 4 years later. Found an excellent welder who knew their trade both times. They both used a TIG with a bronze alloy rod to do the repair and trust me, they will not break again!

concours · Aug 15, 2014

commando6868 said:
concours said:

Mike, my repair outlined here: engineering-compromises-leading-exhaust-threads-stripped-t14363.html?hilit=Exhaust

YMMV

Click to expand...

Good info, so far I haven't stripped any threads. It's still early tho.

MF

Although wallered out threads was the topic, all the same stuff is what causes the pipes to break. The "orbit a 5' length of tubing with a muffler on the end" is the root cause.

I was 75 miles from home, with 200 yet to do, (2012 INOA Rallye) when my pipe cracked off.

A borrowed squirt gun and 40 minutes to R, R & R did the trick.

pipe broke

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