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[Oudaios]

Hi folks. Thank you for all the suggestions. Alan R - This would not be the first helicoil repair I've done - had to fit two in a secondhand cassette I was refurbishing and I was really pleased with the results; however, I do have to admit tapping the crankcase is out of my league.

PeteF - I have looked into thread repair kits and Loctite's Form-A-Thread looks an option - my biggest concern would be dropping the compound into the oilway as it cures but I have to say I will make a note of it for future reference as it looks like a good product.

I've found a local Enfield specialist who's going to fit a helicoil. Norm - as the engine is still in the frame he's going to remove the head and drill / tap the hole in situ. I'm hoping he has a great trick for not getting swarf in the case. Dennis C, I'm guessing your method with the grease will be used.

Many thanks again - you guys are great!

[simon]

It's not the concept that's wrong Pete just the chemicals. The loctite products are generally cyno acrilates for the hard setting ones the flexible ones are possibly something else but not epoxies. I personally hate helicoils and would try the glue first. It's not like you won't spot it if it fails. Your oily shoes will be a signal.

[Dennis C]

Simon, why do you hate helicoils?.

[simon]

I know they have their place and I've used a few over the years. But I've also come across machines that have been blighted with them and they do fail. Either they unscrew or they get loose and cause all sorts of mayhem. If a thread irrevocably strips ( often times I've saved one using a fatter fastening in the same hole) I generally prefer to make a threaded sleeve tapping the hole out to the next size up and screwing in (with Loctite) a brass or steel insert with the right thread on the inside. I mentioned on a different thread about my Ducati 860's clutch cover which has Allen screws holding it on. They've tended to flog out over the last 39 years and helicoils aren't good with small threads that get undone a lot so a quick tap out to 8mm and a brass tube with an 8mm external thread and a 6mm internal can be screwed in chopped off flush and gently filed smooth for a lovely tidy and re reparable (should such a thing be necessary ) solution.
With my old 51 Bullet on the other hand I had some of the timing covers fastenings supposedly stripping. When I measured the fastenings I discovered that they had been made undersized (several thous under 1/4" possibly due to the plating process?) so I made a new set of slightly fat ones and never had another problem. So no helicoil, no stainless nylocks and no pk's. Unless of course nothing else is available.

[Dennis C]

Hi Simon, Thanks for the reply, I agree that a threaded insert can make a good and permanent repair but the same goes for a Heliciol repair if done correctly, as with the threaded insert a Heliciol should be fitted using thread lock and when done correctly will make a thread in aluminium stronger than original.



I have used the insert method to bring threads back to standard when previous owners have overbored the hole and fitted bigger bolts/studs, call me pedantic but I feel fitting bigger bolt/studs is little more than a bodge.

[Midge]

Indian crankcases do seem to be made of cheese. Mine is currently in two halves receiving some serious repair work. Cleaned and inspected closely, there are many casting defects almost as if when they were cast the mould wasn't hot enough. Inside is worse, evidence of casting flash being chiseled off. Never mind, photos and report will follow in due course.

[simon]

The castings on my 92 350 motor were incredibly rough. I took off masses of aluminium with a bastard file and a scraper. The alloy seemed fine and the machined surfaces were all good but the moulds were obviously very old and worn and there was no factory fettling done. At one stage fettling the timing case cover I popped through into what I at first thought was an oil way but turned out to be a blowhole in the casting. I filled it like a dentist with the fillings mixed with superglue which produced an almost invisible repair.

[loco builder bri]

Denis is correct a helicoil is actually stronger than the original.They are often installed straight away
to components subject to very regular maintenance, But never with loctite.
In my experience the use of Loctite on a helicoil often leads to the helicoil coming out as the screw or fitting is undone resulting in further damage to the threaded hole!