EXHAUST PORT RE-THREAD

Thanks for sharing, I'm probably going to need this soon! I've had aluminium inserts welded in before, but never been happy with them, and one of them's on its way out. I've been wondering who might use the method you describe, this side of the pond â Jim Comstock offers a similar service in the US, but I don't think I'd fancy the shipping costs ...

Can we ask what he charges?

Actually, so long as it didn't change the appearance too much, I'd much rather use a 'studs-and-collar' solution, as used on '70s/'80s Kawasakis and Suzukis that I remember, no doubt others too â so much less bother ... Copper grease on the studs as they go into the head, and the same on the outer ends of the studs for the retaining nuts. A complete joy to work with by comparison, and I'm pretty sure I've seen that someone's done this on one of our Nortons ... I'll be blowed if I can remember where, though!

Previously allan_brooks wrote:

Previously Colin Peterson wrote:

Actually, so long as it didn't change the appearance too much, I'd much rather use a 'studs-and-collar' solution, as used on '70s/'80s Kawasakis and Suzukis that I remember, no doubt others too â so much less bother ... Copper grease on the studs as they go into the head, and the same on the outer ends of the studs for the retaining nuts. A complete joy to work with by comparison, and I'm pretty sure I've seen that someone's done this on one of our Nortons ... I'll be blowed if I can remember where, though!

Hello Colin with mine you cant see any of the insert once the rose nut is in

Hi Allan, thanks for the response â yes, I don't doubt that the insert is invisible once the rose nut is in. What I was getting at is that I find this entire approach to securing the downpipe into the exhaust port to be a royal pain, inflicted on us by Norton. I'm attaching a couple of images pinched from http://www.zedrider.co.uk/exhaust-system.html (q.v.) to illustrate what I'm blethering on about above â which is, doing away with threaded exhaust ports entirely, and using studs and clamps instead. As I said, I'm pretty sure I've seen this done with one of our Nortons, somewhere online. I've found this method to be so much easier to live with, and to work with, on Japanese bikes from the late '70s to mid '80s, although of course I've no idea how practical it might be to convert a Norton head to use it.

p.s. I loved my Z650 and wish I still had it â but I love my Norton more.

I've seen it done on Norton heads. I have an idea that it might have been featured in 'Motorcycle Mechanics' during the 1970s. The only realistic way of doing it is to drill up through the fins and insert a cross-bored trunnion on each side. which the retaining bolts can be threaded into. OK if hidden behind an Interpol fairing but not really an improvement to the lines of the Norton head.

Springs such as used on race exhaust systems can work quite well, but nothing looks as nice as the standard set-up.

Previously Colin Peterson wrote:

Previously allan_brooks wrote:

Previously Colin Peterson wrote:

Actually, so long as it didn't change the appearance too much, I'd much rather use a 'studs-and-collar' solution, as used on '70s/'80s Kawasakis and Suzukis that I remember, no doubt others too â so much less bother ... Copper grease on the studs as they go into the head, and the same on the outer ends of the studs for the retaining nuts. A complete joy to work with by comparison, and I'm pretty sure I've seen that someone's done this on one of our Nortons ... I'll be blowed if I can remember where, though!

Hello Colin with mine you cant see any of the insert once the rose nut is in

Hi Allan, thanks for the response â yes, I don't doubt that the insert is invisible once the rose nut is in. What I was getting at is that I find this entire approach to securing the downpipe into the exhaust port to be a royal pain, inflicted on us by Norton. I'm attaching a couple of images pinched from http://www.zedrider.co.uk/exhaust-system.html (q.v.) to illustrate what I'm blethering on about above â which is, doing away with threaded exhaust ports entirely, and using studs and clamps instead. As I said, I'm pretty sure I've seen this done with one of our Nortons, somewhere online. I've found this method to be so much easier to live with, and to work with, on Japanese bikes from the late '70s to mid '80s, although of course I've no idea how practical it might be to convert a Norton head to use it.

p.s. I loved my Z650 and wish I still had it â but I love my Norton more.

Hello,

This is a bit along the same topic. I used the 8mm copper nuts VW used on their air cooled 1600cc flat fours. They are the same threads as the ones used by Kawasaki and Yamaha and will not seize up...Ever.

I also love my Norton model 19S. But since you brought it up.

Previously richard_payne wrote:

I've seen it done on Norton heads. I have an idea that it might have been featured in 'Motorcycle Mechanics' during the 1970s. The only realistic way of doing it is to drill up through the fins and insert a cross-bored trunnion on each side. which the retaining bolts can be threaded into. OK if hidden behind an Interpol fairing but not really an improvement to the lines of the Norton head.

Springs such as used on race exhaust systems can work quite well, but nothing looks as nice as the standard set-up.

Would it not be possible to weld up bosses between fins to take studs? If so, then you'd just have to source finned clamps of a suitable size, and if necessary cut a couple of bits of tube to act as spacers between the clamps and the flanges on the downpipes â? Just a thought.

I don't believe there's anything fundamentally wrong with the threaded exhaust ports. I had my first Commando 850 done by Alf Snell in Boundary Road. London (is he still there?) but my second which I had for 20 years never needed any attention. The threaded exhaust port goes back to Vintage days and to my mind works perfecltly well.

The problem is with making it Japanese style is where do you stop?

Thanks Ian, but, when you say you 'had [your] first Commando 850 done', you're referring to exhaust port thread repair? Here, I'm really just indulging in an electronic form of thinking aloud, and looking for helpful responses, even if they're along the lines of 'it can't be done'. Those threads, as they are, have been a bane to me. If you needed a repair once, even if it was more than 20 years ago, then you know there's a demand for that at least. And I can certainly see myself going for the threaded-sleeve-insert method outlined in the first post in this thread. I'm just wondering about a third way, one that I personally would prefer â if it didn't alter the appearance too much.

As far as 'the problem' is concerned, isn't that material for a different topic? I'm thinking 13mm master cylinders, converting pre-MK3 Commando swinging arm attachment to MK3-style, fork damping mods, and the list goes on â? Cheers.

Why not get it Helicoiled by RGM? Inserts in an ancient, cast-alloy head seem like bad news to me, no matter what they are made from. Taking material from the head isn't good whereas Helicoiling removes a minimal amount by re-tapping. The insert is a hard material too, so even when your pipes go walkabout and rattle they are much less likely to get damaged.

Previously lionel_yexley wrote:

Why not get it Helicoiled by RGM? Inserts in an ancient, cast-alloy head seem like bad news to me, no matter what they are made from. Taking material from the head isn't good whereas Helicoiling removes a minimal amount by re-tapping. The insert is a hard material too, so even when your pipes go walkabout and rattle they are much less likely to get damaged.

Thanks, Lionel, it hadn't even occurred to me that these threads could usefully be helicoiled! I expect it's fairly cheap, too â?? Although obviously I can ask RGM about that myself.

Have a look at Mike Pembertonâs Post on the Norton singles page, he shows how he fixes them.

HELLO we in east yorkshire have John Malone and sons heavy engineering in Goole That alloy welded my pinch bolt side of the fork leg back up and made a great job for 20 notes and he do any other odd engineering jobs there well tooled up for all types of work, in engineering they even make things from scratch , yours anna j

Mike Pemberton's fix looks much like that offered by the outfit mentioned in the first post, and by Jim Comstock in the US, unless I'm missing something â?? Anna, thanks for the tip.

RGM say they charge £57 plus VAT to helicoil each port â for future reference, it's their part number 050127. Allan, was that £150 for one port, or for both? TIA

Without wanting to teach people how to suck eggs here, may I offer some advice. I've had two 750heads fitted with aluminium inserts and they haveboth worked a treat. When I fit exhausts I do a dummy run first just to get the fit right. Offer the whole exhaust up to the bike and tighten the silencer up slightlyto the pipe so thatany frame mounting bolts will align closely with their corresponding holes.Tighten the pipe into the head slightly, while leaving the silencerslightly loose on the frame. Once you know that everything will bolt up tight and right, and with the crush washers in, cram the heck out of the exhaust port rose nuts with the Norton exhaust spanner. Doing it this way ensures that the exhausts go into the head straight. Once you have lifted the bike off the ground with the spanner (well almost). you cantighten the silencer to the pipe and thencomplete therest of the assembly. Now go for a ride, heat the thing up, stop at the side of the road and give them a last heave.

I tried locking wire, springs and all sorts, and everything just kept coming loose. Since I had the heads sorted with inserts and started using my fitting sequence I've had no problems at all.

The trouble with locking wire and springs is that they stop the pipes from falling out, but they don't stop them from coming loose. Once they come just a tiny bit loose, they vibrate and wear out the threads, and you don't know it's happening.

Sorry if I'vebored you all fartless.