Exhaust issue

I've been riding my '73 850 Interstate for almost 20 years now, and have been experiencing a problem since the beginning that I have not been able to cure. On any ride longer than a few miles, my left exhaust clamp at the muffler will come loose and slide up the header no matter how hard I tighten it. An inspection will reveal that the muffler flange where it over laps the header pipe will be worn paper thin after a couple thousand miles, but the header shows no wear.

I originally had replica Dunstall mufflers on this bike when I rescued/rebuilt it. When I had those on it, the shims would come out all the time. About 10 years ago, I replaced them with peashooters, I'm on my second pair now, with still the same problem. Before I replace the muffler again, I'd like to solve this.

I've replaced the headers a couple times too.

Iso's were replaced the first time I put the bike on the road when it was wearing out the Dunstalls, I upgraded them to the Mick Hemmings adjustable type 10 or so years ago. I've adjusted them at least once a year. Swing arm spindle mod has been done. Upper engine mount has been upgraded several times, Norvil type, MkIII type, and currently one of the hiem joint versions (which upped the steering accuracy alot, I highly recommend it).

The right side muffler clamp has always stayed tight, and the mufflers never show any wear. Something is causing the motor and header pipe to move around, wearing the muffler, but I have not been able to put a finger on it.

If it's just a tightening clamp issue, get some 'Moose' clamps. You can really honk down on those honeys without stripping or bending things. There's another style that's solid, but I've lost the link on them. The one on the right. The others I got from Clubman and the little half cylinders are made of al and don't hold up.

I like your long range load carrying Commando. [don't know why text bolded]
My Combats also make the headers slide/oscillate inside muffler neck and more so on the LH like yours. Prior attempts to clamp well by stronger- better after market clamps didn't work for very long but long enough to fracture the header(s), twice and a few muffler cushion sets. Last ~3 yrs I've left both sides loose as they get, which rattles some to cross rough stuff but makes it easy to remove header w/o removing the muffler. I assume the DS chain tugs on LH isos more the RH.

There are after market clamps that have two clamps, one clamps header the other the silencer to act more like an over lapped splice. Some of these have solid sleeve with two clamps others have a woven steel braid for some flexibility or vibe isolation and I've seen similar in hareward plumbing that has rubber boot surrounded by metal sleeve - yet likely all still too stiff to actually take up the motion element of isolastics range, ~1/8-3/16" with road loads. Shop Harley catalogs like me but the better is stays clamped the better exhaust vendors will like it.

These Commandos were considered a stop gap model so spit out to public w/o all their quirks solved, so have a hand full of extra consumable items other lessor simpler cycles don't have to deal with. Vendors appreciate this no end.

The final solution... engineering-compromises-leading-exhaust-threads-stripped-t14363.html?hilit=Exhaust

Thanks for some ideas, guys.

Holding the muffler/header joint tight at this point would be a mistake, I believe. I too, have fractured headers at the head, probably from cranking down on the clamps and trying to make the whole assembly rigid.

I don't see how the drive chain can be causing shifting to the left. The motor, cradle, and swing arm are all bolted togeather, so should move as a unit. Something is causing the motor/gearbox/cradle/swing arm assy to move to the left as opposed to the right, I just need to figure out what.

In a perfect Commando world w/o clutch basket wobble and swing arm slack the triplex chain flop and drive chain thrusts should not tug the LH iso's to and fro but in real life apparently they can and do, at some point of wear/tear. Tug on your drive chain and/or triplex and observe iso's and header mating in your bike. I'm stuck sticking to part numbers on Trixie discipline so keep a handful of cushions on hand and often waist them like i do the head steady ones. Been through like 4 sets of headers, one from Victory, so still hoping some day to get a set that fits right off w/o banging bending and grinding to make useable.
On my special will try springs 'clamp' to hold the muffler to header and also to suspend the muffler.

AAU's, tires, Amal slides, oil, gas, headers peashooter and ones wits and endurance are all normal/common Commando consumables.

As I remember there's more than a few guys that have mounted the silencer to the cradle, eliminating the rubbers. Would that be an option for you? ludwig for one, I think.

I used to have that sort of problem. Make the slots longer with a hacksaw & use 2 exhaust clamps, it will clamp a lot better.

I had a similar problem to that on another make of bike.
Got a short length of stainless pipe, split it down the side,
and clamped it over the the join with 2 clamps, as suggested above.

Its likely your pipe/muffler are flexing in and out (sideways) while on the move - too much,
and things are working loose.
Maybe a spring could pull them towards the cradle, without actually bolting them solid ?

I'm using T-bolt clamps like the picture from DogT. They are available from Dennis Kirk https://www.denniskirk.com/moose/1-44-i ... 435320.sku but they are pricey or McMaster Carr (cheaper) http://www.mcmaster.com/#standard-tube-clamps/=ngs4z0

Dave

norton73 said:

I originally had replica Dunstall mufflers on this bike when I rescued/rebuilt it. When I had those on it, the shims would come out all the time. About 10 years ago, I replaced them with peashooters, I'm on my second pair now, with still the same problem. Before I replace the muffler again, I'd like to solve this.
The right side muffler clamp has always stayed tight, and the mufflers never show any wear. Something is causing the motor and header pipe to move around, wearing the muffler, but I have not been able to put a finger on it.

Click to expand...

Had an identical issue on my 850. Left side would loosen - Dunstall replica muffler would slip its shims and the whole lot wave around in the breeze. The problem is the shims creeping out between the header pipe and ID of the muffler tube. To fix this, I used a wide band stainless hose clamp on the header pipe butting up to the flange end of the muffler tube, that stops the shims from slipping out. It hides out of sight. Then fitted a heavy duty clamp on the muffler tube (like Dog T mentioned) and thereafter many trouble free miles. I also never remove the muffler from the bike, but rather disconnect from the head and muffler rubbers as a one piece assembly.

Having recently fitted a pair of Emgo Peashooters (Dunstalls making me deaf) the left muffler cracked a weld seam at the header end. This was fixed with a braze weld. The right side is fine. Somehow, there seems to be more stress on the left side. Maybe because the engine is offset in the frame?