Exhaust repair on the move.

Hi all,

So it's all going well until ..(you've been there - it's a Norton)...I decide to adjust the RS exhaust. I've just finished the trans redo, new chain and rear drum, some wiring, switch back from PR clone to Roadster, some additional minor stuff and go to start it after perhaps 8 months of down time. It rewards me with a first kick start and I'm happy but the kickstarter is hitting the muff pretty good. But a short ride is in order and it feels good. Then the attempt to adjust the (aftermarket) pipe on the RS.

The exhaust lock ring is tight but there is some play in the pipe. When I unscrew the ring and remove the pipe I find 2 gaskets in there and it doesn't look right. This is the side that had stripped out the threads in the head many years ago. I took the head to my machine shop guy and he drilled out and then pressed in a threaded replacement. It's been used all this time but the bike doesn't get a lot of mileage. At some point I must have decided I needed two gaskets in there - apparently it wasn't tightening up but I don't remember that. Now, however, I see the problem all too well. The interference fit replacement piece is being pulled out of the head (one might say "extracted") by the lock ring as it tightens down against the head inside. This photo shows the set-up:



This next photo shows the file marks on the outside of the edge of the replacement piece and how they match with the marks on the head:



Its obvious the marks were made at the same time and when the items were flush with each other. That is no longer the case by a factor of about 3/32":


So the question is, what to do? I have a number of items I want to monitor this riding season and hoped to ride the bike for the season, deciding as I go about new shocks, iso work, RITA trade-in, fork redo, etc., which would be done over next winter. I am not thrilled about taking the head off at this point because I simply have too many other projects to do. I'm thinking there are a few simple options without head removal:

1) space it out so it fits/works the way it is and run it/watch it
2) attempt to drive the replacement piece back in using heat/cold/appropriate tools and THEN run it/watch it.
3) grind off the amount now exposed and run it/watch it

If I have to pull the head next winter, so be it. I'm curious as to what your opinion or other idea might be about my "on the move" exhaust item!

Here's a thought as a temp fix.
I assume it is a pressed in piece, right?
Try driving it back in using a socket so as to not damage the outer surface, drill a hole through the head on the left side and tap it for a set screw to lock it in.
If you can get 2 hole drilled, all the better,
And when you do remove the head for a proper repair the holes can be welded up and then ground smooth.
Just a thought.

What Guido said............ +1


Tim_S

I have repaired this same problem on my Commando. It had been repaired in the past by pressing in bronze internally threaded rings. They started to pull out. What I did was drill first drive the insert back in and then I tap 3, #12-24 holes down the outside of the insert so the thread was about half in the insert and half in the head.

Then I got some screws, screwed them in as tight as I could and cut off the heads. This has been good for about 5,000 miles now so I guess it worked.

The best repair for the wrecked threads is to put in an insert that is internally and externally threaded.

At first I tried #10-24 screws. That didn't work. The bigger coarser screw is best, but there is not much room

Nigel

Nigel's repair method was the one I was also thinking about, you could even use grub screws, so you done need to file them off afterward. If you have some machine shop access, I would make up a drill guide. Even a piece of flat with the two holes drilled at the right centres to coincide with the intersection of the insert and the head, and another hole centred between these two so you can attach a plug that is a good fit to the exhaust threads. That will get you two treads in the right palce and you could rotate and get four, which should see the summer out okay. Then off to Comnoz for the proper fix?

Cheers Richard

Thanks all, for the replies! Two very worthwhile ideas - I'm going to check out the possibilities and will let you know how this turns out. First step, though, is to decide whether to drive it back in or cut it off flush. No experience with driving an interference plug back in after it's been pulled part way out. Do you think it will tend to loosen the fit up even more and make securing it temporarily harder to do?

Your fix #2 is the one I vote for. Since the bike will run, fire it up and let it get hot. The exhaust port is one of the hottest parts of the bike. When it is good and hot shut down and get the pipe off there fast and stick some ice on the insert and then placing a flat surface on the insert whack it a couple good ones with a 3 lb. hammer. You'll need to have everything ready ahead of time but if it's coming out when cold by tightening the collar it should go back in easily this way. I'd be tempted to pull it right out and coat it with red loctite then drive it home but maybe that's for next time.

RennieK said:

I'd be tempted to pull it right out and coat it with red loctite then drive it home but maybe that's for next time.

Click to expand...

Thanks, toyed with this idea too but discretion being the better part of valor, think I'll skip the opportunity to generate one of those "DAMMIT!!" moments. Might at least try to set spacers inside to screw the locking ring against to see how easily the piece does pull. Also thought to file a shallow groove around the circumference of the piece and fill that with red loctite before trying to hammer it back in.

I know that you want ride it and not wrench on it, but I'd pull it and send it to "comonoz" and have it fixed right. He's here on the forum. You can do a search and see some photos of his work posted here. Top notch stuff and very reasonably priced. Just my two cents

You're probably right but I'm going to give a "temporary" repair a try. I know of Jim's work, I put one of his reed valve breathers on this past down time, but the planned fix is fairly simple, easily monitored for success or failure and of no real consequence if it does allow the piece to start pulling out again. A legit repair can be done later with very little extra work regardless of how the temp repair goes.

Besides, it's vintage kart racing season and between wrenching for that effort every week and knowing how "simple" Norton jobs tend to metastasize into months-long campaigns, I'd either have to let it sit or do the temp and ride it a bit this summer. It's not a long distance or daily machine - has only 8200 miles on the clock.

So, for those who might find it of interest, I completed the (temporary??) repair by:

1) Deciding to see how tight the insert actually was and what it would take to force it back into place, I used a 2x4 and gave it a medium shot with a hammer and could see it wanted to move fairly easily. Two or three more hits and it was flush. To maximize how far the lock ring could turn into the head, I then used it (threaded into place) to further drive the insert into the head a small amount.

2) I was contemplating making a drill guide but decided I'd take a chance on doing one hole freehand since both items were aluminum. I started the hole right where the insert meets the head and decided to drill angling away from the insert as I drilled since I was worried about deforming the threaded insert when the screws were installed. It was a judgement call on the angle to use since I also wanted to have the screw engage as much of the insert as possible as it went into the head. I was careful not to drill through to the cavity behind the insert, nor to drill at too great an angle.

3) It was easy drilling and controllable by hand without a drill guide. The first hole looked like it would provide lots of area for the screw to engage both the insert and the head and I screwed a sheet metal screw in until it broke off. I did the other three holes and screws the same way:




I realized that even drilling at an angle had produced slightly raised areas near the very inside of the insert's threads where the screws had pushed out the edge of the insert - much like a tree root will do to a concrete walk - but didn't think it would be a major problem and proceeded to clean up the surface:




The lock ring went in easily but did bind on the inside, raised, areas but with some oil applied while screwing the ring in and out a few times, all was well and the pipe went on (I did have to use 2 gaskets again to space everything properly) with no problem and the ring got as tight as I could want with no sign of the insert turning in or pulling out from the head.

Time will tell but as a temp repair (which only took 2 hours from start to finish, including pipe/muff R&R and tool cleanup) I think it will work well and who knows how long it will last? As a bonus, the tightened up system now affords clearance for the kickstarter. Thanks to all who made suggestions, I love this forum.