T100R Spark Plug Hole Repair

My friends newly acquired '72 T100R Daytona, that I agreed to revive from 20 years of storage for him for riding privileges, has thrown another curve at me. The l/h spark plug hole has been repaired with a Heli-Coil that is coming loose and working its way down toward the piston end of the hole. Time-Sert makes an oversize spark plug thread repair kit for failed Heli-Coil repairs, and I have found a place that rents them. I haven't pulled the head off yet, but I'm wondering if there is a spark plug hole to valve seat clearance issue on the 500 Triumph head like there is on the Norton head when doing one of these repairs? Has anyone on here used one of these oversize Time-Sert kits?
Bill
http://vwparts.aircooled.net/Big-Sert-Tool-Rental-14-x-1-25mm-5141S-p/big-sert-rental-5141s.htm

pantah_good said:

My friends newly acquired '72 T100R Daytona, that I agreed to revive from 20 years of storage for him for riding privileges, has thrown another curve at me. The l/h spark plug hole has been repaired with a Heli-Coil that is coming loose and working its way down toward the piston end of the hole. Time-Sert makes an oversize spark plug thread repair kit for failed Heli-Coil repairs, and I have found a place that rents them. I haven't pulled the head off yet, but I'm wondering if there is a spark plug hole to valve seat clearance issue on the 500 Triumph head like there is on the Norton head when doing one of these repairs? Has anyone on here used one of these oversize Time-Sert kits?
Bill
http://vwparts.aircooled.net/Big-Sert-Tool-Rental-14-x-1-25mm-5141S-p/big-sert-rental-5141s.htm

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Comstock has.

drill O.S. tapered , Weld ( TiG ) redrill & Tap , with the wonders of modern tecnology , is less bodgey .

I.E. , Return it to How it Was MADE , is best .

Strewth , a mint bare S.H. or N.O.S. head should be only $ 100 , and a lot less stuffing around .

But Inspect Microscopically befor purchase . To many mongrels have bodged repairs from ham handed ' maintanance ' .

ALWAYS clean the Head & Plug threads with a Paper Towel , ( wraped round a narrow screwdiver , for the plug hole ) and some solvent or petroil so its CLEAN .
Thena slither of greaese , but much better ANTI SIEZE , such as copper coat . Note the plug spanner posn. when the plug SEATS , & stick to the book .

new ones turn further with washer crush , after that its not a quater turn , If the threads are clean . If the arnt clean & your to lazy , stuff up a Honda INSTEAD .

Matt Spencer said:

...a mint bare S.H. or N.O.S. head should be only $100...

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Crikey!! I must be looking in the wrong places. Did find a ebay photo of the business end of one, showing the available real estate between the plug hole and valve seat, which is somewhat encouraging.
Bill

Its mainly early 8 stud ( pre unit ) heads that crack across- plug hole thru valve seat . Late 8 stud 650 theyed thickened so arnt as crinkly .

Yr Picture , many a unit head had ' Central Plug ' or Dual Plug conversions . Offed in ' hot up ' adds as a service .
Usually the new 12 mm plug was located vertical , dead center - Right between the valves , where yes it cracked the head ,

But if you wanted to , bunging the existing plug holes & machining new central 12 mm plug recepticals would be ' period ' correct Ace Cafe ton downt bypass acceptable . :lol: :lol: