Options for stripped threads in the head of 650 exhaust port?

[Speciman]

For years my 1970 Bonne T120 had a stripped exhaust port in the head. The exhaust port won't hold the flange that screws in and holds the tail pipe. I was running TT's when I first got the bike but had to convert over to a 2 into 1 exhaust setup to allow the head to hold the tail pipe more securely. Now I want to go back to the TT's but not for the cost of a remanufactured head. Anybody know of any alternate solutions for this problem? I want that rumble of the TT's back. Sorry for the real old picture. The bike has been in storage for the last 20 years and I only had 1 pic of it before it was taken apart and stored. The 1 pic was a rumpled old polaroid and this is a pic of that pic.

[Lindy]

There was someone on e-bay making oversized self taping spigots might try that route

[59]

i ran with some nurled stubs but eventually had those TIG'd permanent. I know this solution gives some blokes the yips but it was the end to my woes.

[Truckedup]

I read about using a 1-1/4 inch pipe nipple, 3 buck repair job... I tried it,it worked. Get an 1-1/4 black iron nipple about 4 inches long. Screw it into the exhaust port with a pipe wrench or large Channel Locks. Unscrew it and cut off a few thread util it bottoms out and only a thread is showing. Make sure it's tight. Cut off pipe stub to match original,clean away any metal debris.
Depending on your pipe you may have to reduce the diameter of the pipe stub. I did mine on a bench grinder..Do this before the final fitting into the head.

[Speciman]

Thanks Guys. They all sound like feasible alternatives to me. Really appreciate it.

Rob

[Speciman]

Hey guys, it's me again. Thought you and other Triumph owners would like to know that I started with the easiest suggest 1st; Ebay. Then I was going to work my way to the hardest. But, did my search on ebay and BINGO. Some dude, vwalley1, was selling what he termed "repair spigots" 050" oversize on the thread end, with the exhaust pipe end turned down to the stock size. Said he sold over 700 sets worldwide because it is a common problem and has the feedback to prove it (over 6300) without as negative. Also said the Triumph owners on Jockey Journal were raving about them. So, again THANKS.

Just remembered something. Since I would be going back to straight to straight pipes from pipes with a muffler would I have to re-tune the carbs or change the jets?. Can't remember if I did when I made the switch the first time around but since the back pressure will change it leaves someone like me, given my limited experience with big questions.

[TriNortchopz]

Old thread, but found this which may be of interest for a 'permanent' solution to the stripped threads in the Triumph exhaust ports:

TRIUMPH 650/750 TWIN EXHAUST PORT THREAD REPAIR
(both sides)

Seager Engineering
"Using our own CNC machined STAINLESS STEEL insert. we helical interpolate a new repair thread into the head also machining the stub seating face ( this face can be worn and if it is, we machine and fit a stainless spacer to recreate a good seat) and then we fit and lock our inserts into the head. "

http://vi.vipr.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=371807664920&t=1551453103000&tid=310&category=177970&seller=seager-engineering&excSoj=1&excTrk=1&lsite=3&ittenable=false&domain=ebay.co.uk&descgauge=1&cspheader=1&oneClk=1&secureDesc=0&oversion=e0e67cb8

[Guest]

There’s similar repairs on here with aluminum inserts which I prefer. The problem is still there the aluminum head and either this insert or stock stub expand at different rates.

Now we’re introducing the biggest evil in the world, stainless threads, and in the hottest part of the engine.

[TriNortchopz]

Great, I found on a Norton site a guy in Colorado who repairs Norton threaded exhaust ports with hard al-bronze inserts, so the expansion rate of the metals are similar; James Comstock, The Norton Motorcycle Machine Shop: http://www.nortonmachineshop.com/

[Dougtheinternetannoyance123]

The Norton head stripped threads is a totally different enchilada than the Triumphs. We did a head survey years back and found the castings were so variable with the ports varying angles and sizes. Couple that with any Commando has rigidly mounted pipes with the entire motor/trans/swingarm all mounted on rubber isolastics so exhausts on Nortons are a PIA. While Jim does nice work and I know him, he is by far NOT the only resource for Nortons or cyl head repairs.

Now Triumphs are totally different. For a while in the 1970s they even tried the BSA method of no threads at all and jammed in pipes into smooth ports. (Most install adapters). The reason so many Triumphs have a problem is 2 fold.

First, many, not all but a LOT of Triumphs were never properly threaded at the factory. You can see this clearly and fix it with a large bottoming tap. The threads crap out before seating so the insert never is fully threaded in. Clean it and tap it clear the end.

Secondly they insisted on using steel inserts in a Alloy head. (Not a great idea). Heat and vibration loosen them, wallow out the holes and bingo. Loose as a goose.

I generally try to clean up the threads and install a blind set screw from the bottom, but if not possible we bought alloy tubing and machine out the port and turn down the alloy tubing and machine to a light interference fit. (Freeze the insert, heat the head) Press together and hold while cooling. Then machine a set screw from the bottom.

Easy.

[farmall]

Sensible too since a worn insert may be easily machined out and replaced in future.