Exhaust Thread Repair

[danedg]

The exhaust nut threads departed company with the cylinder head on my '74 Eldo today. I'll speculate on the reasons later, but the first question is:

Who can I send the head to for a proper repair in the Northeast?

[atavar]

Doesn't sound like anything any good mechanic couldn't handle.  Replacing exhaust studs or threads is not that unusual of a job. 

[cruzziguzzi]

If the nut wandered off taking thread with it - aren't we simply talking about replacing the stud in the head?



Todd.

[rodekyll]

I think this is a loop with the big threaded exhaust collars.  I think he's saying the female threads in the head are stripped. 

[cruzziguzzi]

I think this is a loop with the big threaded exhaust collars.  I think he's saying the female threads in the head are stripped.

Ahhh - then almost ANY good machine/head shop will cut and fit an insert.



Todd.

[danedg]

This is a 1974 850 Eldorado round head with the 48mm threaded exhaust collars tapped into the aluminum heads. The big nut threads in there and holds the header...or it used to. No studs. Threads stripped from head. New material has to be attached and new threads cut for the exhaust nut. 48mm x 1.25 I'll wager.
Not your average mechanics' project.
Is anyone aware of a machinist in the Northeast US who can handle the job?
MGCycle has a shop in Wisconsin that does it, I just wondered if there was somebody closer to the tristate area.

[Tom H]

If there is still thread in the head, but not enough to let you tighten the nut fully, there is a fix that "usually" works.

If you have the stock chrome plated brass nut, you can usually expand it a bit to fit tight in the threads and even cut them a bit deeper. If you have the steel version with the lock ring, I couldn't get it to expand.

The only downside to this fix is that the nut is now married to that head. It will no longer fit in a stock head.

If you want to try this, you need a socket that fits inside the nut snugly, an old one with a taper works best, but any socket will do. I usually start from the end with the notches for the wrench and hammer it in a bit at a time, testing the fit frequently. You may need to work the other end of the nut a bit, but save it for the last fitting. It's easy to feel the right fit if you start expanding from the notched end. When you get it right, it will not wiggle when installed.

Hope this helps,
Tom

[lucian]

Are you planning on removing the head? If so any local machine shop should be able to repair. Napa auto has a full machine shop here in Westbrook Maine and there are many smaller local shops too. Ask your local garage mechanic who they use, I'm sure you will find one nearby. Best of luck with it.

[cruzziguzzi]

It just occurred to me that I had this very thing done years ago. I had it welded up and re-cut with a form of bottoming pipe thread cutter.

Damn, I wish the particulars came to mind! It seemed to be a "standard" thread from a pipe kit I got at an estate/farm sale.

Welded, hand reamed and threaded. The little bit I might have been off was made up for in fitting the down tube. This was on my Norton but I guess the principals apply.


Todd.

[Hahnda]

I have used this place for the repair-

Competition Cycle
5081 N 124th St,
Butler, WI 53007

(262) 373-1122

[danedg]

Thanks Hahnda,

That's the place that Greg Bender mentions on TOT...
I'm in the Hudson Valley NY.

[cruzziguzzi]

On an older or high mileage bike I'd send both heads against them cleaning up one and the other remaining as is.


Todd.

[acogoff]

     I would send it to the guys recommended by MG who have done it before. Why be the crash dummy for trial and error effort, even by experienced machinists.

[Hahnda]

I know you kind of want it have it done locally but I would say its probably best to send them to Competition Cycle that has done quite a few of them and knows exactly what to do. I think Harper's also does the fix.

Thanks Hahnda,

That's the place that Greg Bender mentions on TOT...
I'm in the Hudson Valley NY.

[danedg]

They were in great shape when the heads were done a coupla years ago. But I couldn't keep the old nuts tight. That's when I changed over to the new "lock ring" header nuts. When I examined the old nuts against the new this afternoon it occurred to me that the originals are brass and the replacements are steel.
Hmmmmmmmm.......... . 
I'll be checking the left side tomorrow, but I never had any issues over there.
I can only imagine Competition has a jig set up just for this operation...

[TOMB]

Tony and I talked this morning . I have the insert for you. He'll.pick itb up for you
TOMB

[danedg]

Thanx Tom,

I'll be checking with my machinista to see if he can make up a few extras based on your template.

I spoke with Comp Cycles as well. They said no problem. Send the head and the nut so they can cut the thread exactly to match the nut. Turnaround in about a week for $100.

In the meantime, one of my more creative McGuyver's....


A Chinese 1-1/4" cast iron pipe flange that cinches the old nut tight using an old BMW clutch cable and a Tommaselli 2C throttle adjuster tube....

[Tony/CT]

The insert is sitting on my work bench, just need to pick it up, although your repair would certainly stimulate lively conversation at events!!

[TOMB]

The picture shows  good Guzzi ingenuity have to file that for future use
TOMB