exhaust port thread repair

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Oct 30, 2003
Well, the final thread on my motor's right side exhaust port finally gave up the ghost. Has anyone dealt with repairing this problem? As I understand it, the repair can be done by either welding up the old threads and re-tapping them or purchasing an insert which can be installed after a machine shop bores out the opening. I would guess that the threads are probably of the mysterious British-nothing a standard American machine shop has will work-variety. If that is the case then I can forget about using any shops in the Phoenix area. Then again, I've read where the inserts can pull out of the head as the exhaust collar is tightened. I would be willing to ship off the head for the weld repair if anyone knows of a good shop.
Call Phil Radford at Fair Spares America in San Jose, Ca (408) 292-6563 or see the website http://www.fairsparesamerica.com

Talk to him about welding and what it does to the head. The inserts are the best answer. You will need to remove the head and send it to him.
I've done inserts on a '74 JPN (both ports) and a '61 ES2. Both work better than the original threads. Phil uses the type of inserts that can't pull loose when the pipes are cinched down, ask him.

ehaust thread port repair

Thanks for the great advice! I will definitely go the insert route. Also, I finally sprung for a set of whitworth wrenches. After using them on the head, I can't imagine why I waited so long to buy them. We are planning on getting engaged this spring.
Exhaust repairs

There is a shop in your own state that does alot of specialty Norton work.
amr-of-tucson.com/ They are the ons also doing the Nortech anti-wet sump fix. Check em out.
Phil recently rewelded the inserts which had come loose in my 850 head. His advice was to be careful not to overtighten the collars on any head with inserts. I strongly agree with other posts that you should get this work done by an experienced shop.

While you are are at it you should check to see which type of collars you have - the 850 version has about 1/8" less thread than the 750 version - depending on how the inserts are welded the 850 version often does not have enough thread to fully seat the exhaust pipe flange. The slightly longer 750 version usually works better. If you go this route make sure the collar is a good fit with the insert - I'd send the collars to the shop along with the head, or buy new collars from the shop, and have them make sure they fit properly.

NC Commando
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