Exhaust thread repair...

[jbcollier]

Always try a new nut first as it wears as well. My threads were "loose", too but a new nut was all that was required.

Sorry Bob, that is one ugly "repair".

Retighten the nut through several heat cycles. When it no longer requires further tightening, use lock wire to secure it.

Make sure the "muffler" is properly secured as well. If it is waving in the wind, it will take the threads out no matter how much you tighten the nut.

[DewCatTea-Bob]

" Always try a new nut first as it wears as well. My threads were "loose", too but a new nut was all that was required. "

____ I certainly agree about stock ring-nut thread-wear, and his cyl.head ex.threads look so good to me, that I'm fairly sure that his ring-nut is likely over 50% of his loose-fitting issue.
__ Running-up milage with the ex.ring-nut left un-tight, then allows the ex.threads of the cyl.head & those of the ex.ring-nut to wear-down each other !


" Sorry Bob, that is one ugly "repair". "

____ I-myself have only once ever done such a bolt-on/alloy arc-weld type ex.retainer-fix to a Duke-head, and the one I've posted (at bottom of previous page) is not it ! - The one pictured, is of a 350-Road cyl.head which was as-is within a 'lot' of Duke-heads which I once bought years ago.


Dukaddy-DUKEs,
-Bob

[jbcollier]

I'm glad to hear that. I was about to strike you off my Christmas card list!

[DewCatTea-Bob]

____ Well, that wasn't meant to have claimed that the particular repair-job which I had done myself (with added alloy-welding) ended-up looking a whole heck of a lot better than that,, I'm afraid.
However I was rather proud of a similar bolt-on type of ex.repair which I had done without added welding ! ...
__ Instead of adding alloy weld-material, I rather chose to bore 5/8ths-inch holes through the head-finning aligned on each side of the ex.port, then inserted solid 5/8ths-dia aluminum-tubes, which a pair of 8mm retainer-bolts could then be threaded into (instead of added weld-material).
Still not very pleasing to look-at but, rather much better looking than ugly welding-work !


Dukaddy-DUKEs,
-Bob

[Mark]

Hey Blaat, Sorry if it took a long time to respond, I sent a pm to you. The repair I had done at Competition doesn't look like the head with the weld pictured below It is clean and you can't tell unless you know what your looking for. To me, worth the money, it's done right and works. Just me.

[blaat!]

Finally got my head back from Competition Cycle. Took about a month with the holiday season. The cost was $100 for the repair and $15 shipping each way for a total of $130. The repair doesn't look exactly as I expected. They left the weld bead untouched. I'm thinking of milling the face flat and filing the diameter for a cleaner look - I'll need to be careful as I don't know how deep the weld goes. These are the images:

exhaust-thread-repair-1.jpg

exhaust-thread-repair-2.jpg

I have no doubt it is a robust repair, but the appearance could be cleaner. It is a nice weld though. With the exhaust nut in place the area will be less noticeable.

[wcorey]

Not knowing how deep the weld goes, it would be a bad idea to remove much of it at all as that's where all the strength is as far as the insert pulling out (which is supposed to be the issue with this type repair). Looks like the safest place to remove material would be a slight chamfer around it, appears the insert may have been left protruding out of the head a bit and that may have formed a groove for the weld to sit in. You could likely make it flush, doesn't look like much weld would need to be removed for that. I wouldn't be too tempted to compromise structure for minor cosmetics, if you just blend it a tiny bit and even it up I doubt you'll notice it when assembled. But of course you know all this already... Have you talked to them about it?

Bill

[blaat!]

I think you are right about their repair method Bill - I used a sanding block to (slowly and carefully) flatten off the end. Then I filed down the diameter as the weld was slightly overhanging in some areas. That left an area at the outer edge where the unfinished weld bead formed a small chamfer. I carefully sanded that down by hand to make it even and consistent. The repair now looks clean and intentional and I actually removed very little material.
-Jim

[Mark]

The welded bead stays because they machine just enough to drop a threaded collar in that expands to fit the opening. If you want to clean it up a bit I would just make the weld flat enough to have the exhaust nut fit properly to hide it. At the very least you have a head that you can use.