Exhaust thread repair failed

Those two set screws paralell with the port are JACKING screws, as far as I can see.
Ammi missin it?
 
A jacking screw, as I understand it, would be something that would force the insert outwards.
The two set screws going in parallel to the port, split between the insert and the cylinder head.
They don't provide a lot of strength, but I had already set myself up to install them so I went with two per port.
The screws in through the fins, I believe, are my true anchors.
 
TRV8 said:
A jacking screw, as I understand it, would be something that would force the insert outwards.
The two set screws going in parallel to the port, split between the insert and the cylinder head.
They don't provide a lot of strength, but I had already set myself up to install them so I went with two per port.
The screws in through the fins, I believe, are my true anchors.
Click to expand...
....ah, "Dutchman"
 
Dzldanz said:
I hope you are happy with your repair. (Dan Poitras, Precison Cycle)
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Hi Dan.
Yes it all seems to be holding together perfectly. I was concerned the head had too much material removed by a previous owner to fit oversized, left hand threaded collars. Your threaded inserts and careful machining did the trick.
 
Hi guys,

As for my two cents:
Any knowledgeable weldor that is worth his money would be able to weld without inducing distortion or crack sensitivity
Agreed on the commando casts (in particular in comparison to A65 heads) quality wise the foundry work is a old school disaster full of pores etc
But nonetheless welds are doable with a modern Inverter welder.
In my personal opinion and as well experience those heads are reliably weldable without any greater problems.
For welding rods i would recommend 4043, 4047 and due to my current trials 4943.
If inverter machine is set up with correct settings adapt to the weld location chamfering is not necessary.

All the best and kind regards
Christian
 
ludwig said:
The extra support will help to hold the headers, but will put more stress on the mufflers.
Click to expand...
I may end up going with a cradle mounted bracket.

"Ludwig made a cradle mounted bracket that did away with stock Z plates and associated detritus."
From here:

Exhaust header supports? (2014)

About ready to put on new headers from CS. Got new nuts / crush washers and my threads seem OK, although one pipe was a bit loose when I removed it. Wondering if anyone sells, or has fabricated a double clamp support for the pipes in the area near where the headers meet the mufflers. Seems like...
www.accessnorton.com www.accessnorton.com
norton.jpg
 
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TRV8 said:
The exhaust thread repair that was done by the previous owner of my 1973 850 Norton failed. An aluminum insert was installed in the head then welded in place. The weld failed and the insert pulled out, one side only, Hopefully, you can see the photos in the Imgur link below.

When I cleaned things up, I found the fit between the insert and the head to be very loose. The carbon deposits in that area on my initial disassembly indicates that. I would have thought to be a press fit.

Now where to go from here? I've contacted James Comstock, but I don’t believe his usual process of repair will apply here, that is, installing a brass insert. Can anyone suggest alternatives?

Included are photos of the cleaned up exhaust port showing how little material is left in that area.

Any help would be greatly appreciated.
Regards,
Ken Hiebert

View attachment 85580View attachment 85581View attachment 85582View attachment 85583View attachment 85584
Right side, still intact:
View attachment 85585
Click to expand...
Probably pretty late but I can certainly fix it. It looks better than a few I have done. Jim
 
That can be welded back to size by the right guy with knowledge, skill, and fearlessness.
That said I'd probably just buy a replacement.
 
I made the trip to Ottawa yesterday and picked up my head from Precision Cycle.

Dan did a great job installing a thread insert in the exhaust port. He actually had the head done the day after I dropped it off but his usual lead time is "less than a week".

Exhaust thread repair failed
 
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