Plug thread timesert came out twice!

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Plug thread timesert came out twice!
Plug thread timesert came out twice!

Here's the plug hole in question , have you an idea of why they failed Jim?
 
auldblue said:
View attachment 4620 View attachment 4621
Here's the plug hole in question , have you an idea of why they failed Jim?
Click to expand...


It looks like the threads were cut right up to or into the valve seat. Your lucky the valve seat has stayed in place.
High temp locktite may have held the insert in when the threads were new and tight. I doubt that it would help now.

If you were to send me the head I would probably tell you to find a replacement since that looks like a fairly common head and a repair that I could stand behind would not be cheap.
 
Fortunately I have not experienced this problem. Can you explain how the two repairs failed?
Did the insert unscrew when removing the spark plug or did the insert-head joint fail under running engine compression?
Thanks for any details you can provide.
 
The first cert came out with the plug , it was a kick hemmings repair in 2012 , although I was informed that the repair was probably farmed out. The second was loose in the head after only 150 miles, the guy that put it in said at the time "you may be lucky" I wasn't .

Cheers for that Jim , I had hoped for the best but feared the worst , Norman did say it depends how much room you have. May as well do the whole top end and have a deko inside the cases, or swap the whole motor! Bugger
 
AuldBlue .... saw a collection of Norton 750/850 parts on Kijiji in Quebec yesterday 2 complete engines , 2 frames and what looked like enough pieces to build 3 bikes .... maybe he would sell one of his heads looked like he had extra .... the entire lot was $5000 .... I got to learn not to browse on that site , easy to get my old brain in dream mode .... anyways , Good Luck with it !
Craig
 
Just a thought, and possibly too late for you Auldblue, but wouldn't it be possible to shrink fit a solid bronze plug into the hole then tap it for a 10mm long reach plug instead? (and even possibly centralize it between the valves).


cliffa
 
Cheers Craig , I'll get stuck in , soon. I've got all the parts ready and a fresh head built up.
 
Ugh, what a drag to face, twice so far. Since comnoz looked in, I must ask, do heads ever get so bad they can not be recovered in plug area?

Going by what's been posted, alu removed with weakened surrounds, intruding into valve seat security - would it be stupid to suggest pluck the seat out, Muggy 600' F tough alloy fill in, w/o heating surrounds to dis-temper it - like 1 melt weld does 1150'+F, then cut new threads and new seat to get going again with least bleeding?

If it was mine, I'd take head down to only non alu items, valve seats, send to cyro temper shop, which will internally compression alu so much, like shot peening to its very core, plus squeezes/pops valve seats right out no tool hassle, then proceed to hobot obnoxious down dirty deeds. Comnoz was the 2nd one to back up hobot on timeset install length issue to check, so your call or new head eh.
 
hobot said:
Since comnoz looked in, I must ask, do heads ever get so bad they can not be recovered in plug area?
Click to expand...

Anything can be repaired, it is not always equitable or wise,

but with enough money or time you could probably build anything with a welder and a file.....
 
LOL comnoz if that ain't a back peddling cover your ass remark! I was alerted on other forums 15+ yr ago, on cascades of head issues and life, to seek out a decent extra head, just in case, which saved Ms Peel, so hope we will all learn what it will take in this instant case. If there's not enough meat left to put another thread repair insert in, what would you do? Have you not encountered too damaged heads, porous, fracture, repeated weld weakened etc, it was un-recoverable? Melt down to re-cast is not a recovery, but total loss failure. Are my unusual suggestions un-workable?
 
hobot said:
LOL comnoz if that ain't a back peddling cover your ass remark! I was alerted on other forums 15+ yr ago, on cascades of head issues and life, to seek out a decent extra head, just in case, which saved Ms Peel, so hope we will all learn what it will take in this instant case. If there's not enough meat left to put another thread repair insert in, what would you do? Have you not encountered too damaged heads, porous, fracture, repeated weld weakened etc, it was un-recoverable? Melt down to re-cast is not a recovery, but total loss failure. Are my unusual suggestions un-workable?
Click to expand...

Sure I have a shelf full of heads that were not repairable- at least not repairable for less than another head could be purchased or where the long term durability was in doubt.

That is not to say they can not be repaired -and someday it may become equitable to go ahead and repair them.

Of course I have done some repairs for customers who's desire to have all original parts was worth whatever it took to fix them. Anything from cases brought to me in a bag of broken pieces after a rod let loose to an old head that someone had bandsawed the front corners of the head off all the way back to the base of the exhaust threads, fins rocker boxes and all.
 
Jim, I/we love to hear from such competent restorers so appreciate you admitting there's some heads beyond reasonable - till new technologies come on line. Ceramic 3D printing coming online to re design head for small chamber, good valve angles and still look like Norton.
Btw if running low on spares, Baxter Cycle in Iowa has an Commando dedicated warehouse with hip high pile of em, not counting ones still on piles of whole engines. Baxter's week end rallys are about as big and attended as INOA's except way more variety of vintage and modern wonders show up.

https://www.baxtercycle.com/?gclid=EAIaIQobChMI5oz566Gx2gIVxgJpCh0owwsBEAAYASAAEgIi2vD_BwE
 
Could an aluminum or bronze insert be made as Comnoz has said he has made for a smaller plug in the past.
The O.D. of the insert could be made as a 3/8" National Pipe taper.
I think this will allow limited removal of the pulled threads in the spark plug hole.
The striped hole would need to be cleaned up with a tapered reamer to allow the tapered tap to work.
This would give more of a wedged in (Morse taper ,mechanical type fit) engagement.
If the insert was made of hex stock, it would give a place for a socket to tighten it into the hole.
What stands proud of the head in the combustion chamber could be ground off with a dremel type tool.
What is left of the hex stock could also be ground/machined back or a plug with a longer reach used.
Just food for thought.
 
franko said:
Could an aluminum or bronze insert be made as Comnoz has said he has made for a smaller plug in the past.
The O.D. of the insert could be made as a 3/8" National Pipe taper.
I think this will allow limited removal of the pulled threads in the spark plug hole.
The striped hole would need to be cleaned up with a tapered reamer to allow the tapered tap to work.
This would give more of a wedged in (Morse taper ,mechanical type fit) engagement.
If the insert was made of hex stock, it would give a place for a socket to tighten it into the hole.
What stands proud of the head in the combustion chamber could be ground off with a dremel type tool.
What is left of the hex stock could also be ground/machined back or a plug with a longer reach used.
Just food for thought.
Click to expand...




I have used a NPT fitting before with a 10mm plug in it. It worked OK.
I don't think it would do much good once the hole is that far oversized.
 
Cheers Cliff for that , you know I would much rather keep the same head on the old girl.

Fitting a sleeve machined for a smaller diameter plug was suggested by the engineer who fitted the second timesert, if the head is near scrap anyway why the hell not give it a bash, .... For the sake o' auld Lang syne.
 
Jimmy, yes it would be kinda nice to keep the old head.

However, if I understand Comnoz correctly, the risk you have is that the large plug hole, now SO close to the valve seat, has weakened the grip the head has on the valve seat.

It would be rather irksome to rebuild your bike... only to drop a valve seat and write off the top end of the motor, and a con rod, and etc a few miles down the line...

Jus’ sayin’...
 
Aye yer right Nigel, I had a chat with Norman this morning jobs a good un' , fresh barrels , new stock Pistons , decompression plate, combat head
 
Plug thread timesert came out twice!
It's untidy looking at the exhaust threads but it'll do the job! Now all I need is motivation.
Plug thread timesert came out twice!
Plug thread timesert came out twice!
 
comnoz said:
Anything can be repaired, it is not always equitable or wise,

but with enough money or time you could probably build anything with a welder and a file.....
Click to expand...

Explosion forming of a thermal fit alloy bush may do the trick. No warranty of head survival but worth a try, especially if exhaust threads and valve guides need refurbishment anyway.
You could even join stainless steel and aluminum with this method.

-Knut
 
Virtually all aircraft cylinders have heli-coil inserts installed at the factory as there's no way aluminum threads would tolerate the constant removal and replacement. They're not your run of the mill heli-coils, however as they're a serrated design. I have seen a couple back out but they were on old engines that were probably reworked at one time or another. those cylinders were replaced. I also had one back out due to the cylinder being cracked at the hole. It was a bottom plug and I may not have spotted it had the insert not come out. Should an aircraft plug heli-coil get damaged they have to be replaced with an oversized unit. The diamond shaped wire is actually oversized and it's installed with an oversized tap.

Normal torque on an 18mm aircraft plug is 30 lb/ft.

They don't go in like a normal heli-coil and require special tooling. Most aviation spark plugs are 18mm but there are 14mm on Franklin engines and the tools are available for 14mm:

https://www.aircraft-tool.com/shop/detail.aspx?id=4260-14

I've often wondered why this technology wasn't applied on our engines right from the factory as it couldn't have added that much cost during production. Airplane plugs are constantly being removed and replaced for inspection and cleaning and the heli-coils are high reliability.
 
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