[ace.cafe]

I’ve made the bracket from a universal steel one I had in the garage, once that is welded on the problem might not be so bad.

But what do folks find to be the best sealant for the joint? It’s a shame there isn’t an official recommendation.

It shouldn't have problems holding silicone sealer if it is fit in tight against the exhaust port. It only blows out if the fit isn't tight against the port exit.

That said, silicone usually only holds for about one summer of riding. The strip of aluminum lasts forever.

[c1skout]

This has been an ongoing problem with my bike too. I keep my own service records so I know that about 1000 miles is the longest I've managed to have a non leaking exhaust in the 20 some thousand miles I've run it. I've cut the brackets to get the pipe as straight as possible into the port, tried aluminum cans and flashing for shims, different RTV and exhaust sealants. Everything has failed eventually. I'll try rigging some springs on it eventually.

[Paul W]

My upswep' exhaust does have a peg for a spring but as standard there's no way of attaching one. I think one way of doing this is to drill vertically through the fins from above and put a stainless steel dowel in. It will need the head taking off though, to get access for the drill bit, the top frame tube is in the way. So I'll probably do this "next time"..... which of course will probably now be sooner than otherwise needed.... I'm thinking ally barrel now, of course 

[Adrian II]

...and a Super Meteor Sports piston?

A.

[Paul W]

May.....be. But other projects will have to take first priority. I think I need to raid my piggy bank in a serious way before my car will pass it’s next MOT test. I was fitting new rear brakes and discovered structural rust.....

[Paul W]

It’s done it again! The grey silicone lasted all of 100 miles and the aluminium strip blew out.

[ace.cafe]

It’s done it again! The grey silicone lasted all of 100 miles and the aluminium strip blew out.

You must have a larger-than-usual dimension in the head where th pipe pushes in.

Have you tried to use 2 wraps of aluminum strip to seal it tighter?

There is no paste or grout remedies that I have seen which works any better than silicone. They are all temporary fixes. The aluminum strip is the best thing I found.

If you have a muffler shop near you, you might ask them to use their pipe expander to expand just the end part of the header to fit tighter in the head.
The chrome plating would probably crack where it is expanded, though.

[Paul W]

If you have a muffler shop near you, you might ask them to use their pipe expander to expand just the end part of the header to fit tighter in the head.
The chrome plating would probably crack where it is expanded, though.

Yes, I do (as mentioned in my original post). If he can’t cure it, once he comes out of self isolation in a few weeks time, I’ll have to get him to fabricate a new system in stainless which is more rigid and better supported.

[Paul W]

I think I've found a temporary solution, along the lines of the general consensus of opinion. I happened to find a strip of thicker, soft alumin(i)um in the form of a greenhouse window pane locating strap. Along with more "fettling" (i.e. bending using an adjustable spanner) of the front bracket of the factory downpipe I managed to get it more secure in the port. The strip of ally fits much tighter in there (had to hammer it gently in using a flat nosed punch). Along with a good amount of silicone sealant it seems to be holding for now - no popping back. The bike is much nicer to ride now.

I'll get the high level pipe modified as already discussed.

Thanks for the input, chaps!

[Royal Stargazer]

I've had good luck with the silicone, though if it gives, I'll have to give the aluminium can shim a shot.

I'll admit, I knew I had an exhaust leak before I put in the silicone bead by virtue of the fit being just push in, but I wasn't aware how bad it was.

[Paul W]

Without a shim, the both of the two different down pipes I've got for my 350 have enough clearance to rattle in the port once the sealant has gone. I'm considering fitting a finned "cooling ring" at the top of the downpipe in the hope that it would help hold the shim in place.

Now here's a thing: I looked on eBay for a finned exhaust ring. Searched for "nearest first". One came up, supposedly 35 miles from me. Looking in more detail, the seller declares himself to be in Aberdeen (north East Scotland). That's  approx. 390 miles from here. However, looking in even more detail, the seller's address is:

A4/238 Paschim Vihar
110063 New delhi, DL
India.

Lying bar stewards - I've been caught like this before. The item in question took weeks to arrive. Not only that, it had been intercepted by customs and I had to pay import duties of more than double the cost of the item!

[AzCal Retred]

I've had luck sealing the exhaust using the chromed steel finned 1 3/4" "Exhaust Pipe Cooling Ring"; Hitchcocks PN# 26281, and a twisted loop of #10 fine stranded copper electrical wire. I put the cooling ring on the pipe, secured the pipe, twisted the wire around the pipe between the ring & the head, then tapped the ring up against the flat face of the exhaust port. I cut the "tail", the twisted portion of the copper wire, to about 1/2", then aligned it with the open split of the ring. The stranded copper seems to fill irregularities adequately and really restricts the amount of blowby, absolutely better than the plain pipe. Sealing a plain straight wall pipe into a straight wall hole seems doomed to fail, you'd need some sort of packing/gasket material and a way to secure it; the OEM installation has nothing. The cooling ring gives you an adjustable backstop, and the fine stranded copper wire has enough "smoosh" to take up the gap. The steel ring has held up well as opposed to the alloy ring which blew up on the first tightening. The Bullet isn't exactly a featherweight racer, so steel is good enough for me and my 24 BHP iron steed.

[mrunderhill1975a]

I would like to see a photo of that if you have one.

[Paul W]

I've had luck sealing the exhaust using the chromed steel finned 1 3/4" "Exhaust Pipe Cooling Ring"; Hitchcocks PN# 26281, and a twisted loop of #10 fine stranded copper electrical wire. I put the cooling ring on the pipe, secured the pipe, twisted the wire around the pipe between the ring & the head, then tapped the ring up against the flat face of the exhaust port. I cut the "tail", the twisted portion of the copper wire, to about 1/2", then aligned it with the open split of the ring. The stranded copper seems to fill irregularities adequately and really restricts the amount of blowby, absolutely better than the plain pipe. Sealing a plain straight wall pipe into a straight wall hole seems doomed to fail, you'd need some sort of packing/gasket material and a way to secure it; the OEM installation has nothing. The cooling ring gives you an adjustable backstop, and the fine stranded copper wire has enough "smoosh" to take up the gap. The steel ring has held up well as opposed to the alloy ring which blew up on the first tightening. The Bullet isn't exactly a featherweight racer, so steel is good enough for me and my 24 BHP iron steed.

Unfortunately my Woodsman exhaust pipe has a step in it, right at the top, so although I could fit a 1 3/4” cooling ring, the adjacent part where it enters the cylinder head is only 1 1/2” in diameter. The ring wouldn’t push against the shim/wire so I have to rely on a sealant of some sort. I have bought a 1 1/2” cooling ring for the original down pipe but at the moment the ally shim and silicone seems to be holding fast.

[AzCal Retred]

Here are photo's of my stone axe fix. The idea is to fill the void with small copper strands & pack them into the gap, slowing leakage to an acceptable rate. This stopped the downhill-throttle-closed-backfiring syndrome for me. The steel ring is robust enough to survive a bit of judicious tapping to tighten up the gap.