Exhaust thread repair...

[blaat!]

I'm about to send my head out to Competition Cycle to have the Exhaust threads repaired. The cost is $100 plus about $25 for shipping each way, for a total of $150. I understand that they machine out the old threads, press in a new threaded aluminum sleeve, weld the seam and then machine the weld bead off for an invisible repair. Anybody had this done by them or someone else? Any other way to have this repaired?
Thanks!
-Jim

[ajleone]

keep us posted. I would be interested in the results. Thanks,
Tony

[DewCatTea-Bob]

By: blaat!...
" Any other way to have this repaired? "

____ How about a close-up pic of your ex.threads ?
Often they can be simply fixed-up with a Guzzi ex.flange-nut. - (The cheaper way to go.)
__ I've posted a couple pix of a repair-job similar to that brought-up here.

Dukaddy-DUKEs,
-Bob

[machten]

I understand that they machine out the old threads, press in a new threaded aluminum sleeve, weld the seam and then machine the weld bead off for an invisible repair. Anybody had this done by them or someone else? Any other way to have this repaired?

I've had this done twice on bevel twin heads, and in both cases the results have been excellent. (Mind you, this machinist is top shelf and works on old ducati's all the time and is an ex VeeTwo machinist so understands the alloys used very well). It is pretty much totally undetectable and I have had no problems with either of them since.

Kev

[machten]

I understand that they machine out the old threads, press in a new threaded aluminum sleeve, weld the seam and then machine the weld bead off for an invisible repair. Anybody had this done by them or someone else? Any other way to have this repaired?

I've had this done twice on bevel twin heads, and in both cases the results have been excellent.

Actually, I think I need to correct myself on this. As I had the headers off the bike with one of heads that has been done most recently, i thought I'd take a picture of it to post. On examination of this one, and after discussion with a friend that has also had one done recently, it seems this current method is to bore and oversize thread the original metal, then manuafacture an externally threaded sleeve to match (with internal threads to fit the header nut). This is then threaded in and locked with a locking compound, centre punched, and that's it. Pic below...



Seems to be be working pretty well after about 5000km, anyway.

Kev

[blaat!]

Below is a "before" picture of the threads. The exhaust nut currently drops in most of the way without threading it in. I'll post an "after" picture with a total when I get the head back.

This is Competition Cycles contact info:

Competition Cycle inc.
5081 N. 124th Street
Butler, WI 53007
262-373-1122

IMG_7907.JPG

[DewCatTea-Bob]

" Below is a "before" picture of the threads. The exhaust nut currently drops in most of the way without threading it in. "

____ I'm led to very much suspect that your stock ex.ring-nut's threads are also rounded-down, rather badly ! _ Cuz I've seen cyl.head ex.threads in far much worse condition than that which you're showing (above), and yet a NEW ex.ring-nut still grabs the cyl.head ex.threads quite well enough !
Those threads you've pictured are certainly better than many others I've saved, with the use of a new MotoGuzzi ex.ring-nut !
Providing that your posted-picture's view shows the worse side of your cyl.head's ex.threads, then YOUR threads are way too good to have wasted (as you're intending) !
__ The Guzzi ring-nut's threads are taller & sharper-pointed than a Duc.single's, and thus bite deeper into the cyl.head's ex.threads !
Many times after fixing-up really POOR-threads on a Duke-head after fitting a Guzzi ex.ring-nut into them, afterwords I found that a NON-worn stock Ducati ring-nut would then work quite well enough !
With considerably far worse threads than you have, I've first taken & cleaned-out all dirt from within the threads, THEN next very CAREFULLY inserted a Guzzi ring-nut into the ex.port-threads (a little further each try) until threaded-inward all the way in, which after final removal, seems to refurbish the original head-threads so that a new (or GOOD-used!) stock Ducati ring-nut fits & works very near perfectly well !
YOUR cyl.head ex.threads look to me to be like they would do very well after such a thread clean-up job !
You should at least clean-out those ex.threads and try a new stock ex.ring-nut, before bothering with the expensive repair-work you're considering !
Also, I'm quite positive that a new Guzzi ex.ring-nut would very strongly work quite well in those threads you have left !
____ And by the way, is that cyl.head you have special in any way ? _ If not, you could no-doubt get another Duke-head (with better ex.threads) for less than you're willing to pay for that special ex.port machine-work you've been considering !


Dukaddy-DUKEs,
-Bob

[blaat!]

Thanks Bob. Do you have a part number or eBay listing I could reference to find a Guzzi nut that fits?
-Jim

[Rick]

I have a head with the exhaust threads practically gone- worse than yours, and spent some time looking around the net for fixes. The best info I found was here:
http://www.accessnorton.com/documentary ... t4517.html
The welded in inserts do occasionally come loose and get pulled out with the nut. The inside/outside threaded inserts, like Kev's picture, are a step up- the bronze insert looks to be better than an aluminum insert.
I found another head to use for my 'original looking bike', and will probably go with the threaded stud solution that's on page 2 of the Norton forum thread for my worn head.
But, my experience with a twin head may be helpful- when the exhaust threads got too worn to hold, as a temporary fix I welded in little spot beads in a spiral pattern moving into the head, just like a thread. Then I took a nut and cut a groove across the threads, undercut the groove to look like a 1 tooth tap, and ran the nut/tap into the head after grinding down the welded spots flush to the old thread. By leaving the old threads mostly intact I could use them to pull in and guide the 'tap', and since the spots of weld were arranged in a spiral and not a solid band, the nut/tap didn't need to remove much material 'all at once'- I had to be careful since the old threads would be easy to pull out, but it worked, and held for a few thousand miles before I sold the bike. I told the new owner what I had done, and he rode it for thousands of miles before I lost contact with him. Not pretty, but it worked OK, and if I had welded in another series of dots after threading the first set, it would have been better.
Rick

[DewCatTea-Bob]

____ I would expect that an early-70s 750/850-Guzzi ex.ring-nut ought to be available at most any common MotoGuzzi-parts shop.
Just tell them you want the threaded ex.ring with the largest I.D., (as some of them are difficult to get past the curved-bends of most Duke-ex.pipes).



" and will probably go with the threaded stud solution "

____ I have some pix of such an ex.port-modification/repair-job, posted below.