Trouble comes in threes

[bsa-bill]

Just started to put the Rocket Gold Flash head back on after helicoiling the two rear holes in the barrel ( the ones next to the carb), checked the other threads by putting the head bolts in and do the wiggle test.
Turns out this is not too reliable as the front timing side long bolt hole stripped at 20 lbs ft.
However not all together as bad as could be, as I tried the drill that came with the helicoil kit and it will go down through the head so this should be doo-able without taking the barrels off, obviously once the hole is cleaned of its old thread the head will need to come off.
Best I take the rest of the bolts up to torque to be sure before I do anything else.

As stated elsewhere one of the ex valves seemed sticky, so I changed both of them for new ones, it kind of looked like the valves were not sitting square in the seats although a leak test proved good.

We progress - ever so slowly

[muskrat]

G'day Bill,
             good to hear of some progress. I take it that the motor is out of frame. If 3/9 have stripped I'd be worried about the others. I'd hate to take it all back off in 500 miles when you re-tension the head.
 Valve seats need to be re-cut if new guides are put in. If only valves, a quick lap will do. Was the sticky valve bent? If so it might have worn the seat at a bit of an angle, and bellied the guide.
Good luck with it.
Cheers

[bsa-bill]

Hi Muskrat
Have pulled the rest up to 30 lb/ft and they felt good.
the valves might have a very slight bend, tested by sitting the valve upright on a flat surface alongside a good valve and measuring distance at bottom of valve stem and near the top, of course you have to rotate the valve 90 deg at a time and compare, looked like a small but perceptible difference however not too scientific. I could probably get a more definitive result if I put the valves in my bench stand and observe as it turns.
New ex seats have been fitted for unleaded and new guides also, supposed to have been done by an expert, the giudes are not exactly standard not being tapered up to the top, rather parallel, seems to work though

Motor is still in frame, I got the stripped hole drilled tonigh tin situ ( luckily it's not one of the two that are open right down into the crank) and the depth of the hole in the head keeps the drill true, I lifted most of the swarf out with a magnetic probe (carefully).
Tomorrow I'll lift the head and tap the hole in the barrel for the insert.

I found drilling the holes not to be much of a problem as the drill follows the original hole and just removes the old thread.
The tricky bit is keeping the tap true as it starts to go down, you need to be very careful until it gets in far enough that it can't move

[bsa-bill]

Lifted the head this morning and had a rethink, Muskrat's spot on  , for the sake of having the barrels off might as well renew all the threads and have piece of mind.
It's the thought of that sinking feeling when the torque wrench goes slack

[muskrat]

Sorry to give you more work, but better safe than sorry.
Don't think I have seen BSF helicoils down here, or BSC for that matter. Where did you get them? I have a good selection of BSW, UNF/C & metric.
Cheers

[MG]

The only BSC kits/inserts I know of are the ones from "Recoil". IIRC they are actually made in Australia. 

[groily]

 A R Sheldon (in the UK) seems to have a reasonable selection of BSF and other 'armacoils'. . . .? Plus a lot of 'helicoils' in mm and UNF/C. Think the exact search terms used makes a difference to the results maybe as there is a number of suppliers out there. No idea whether one type of kit is better than another though.

[bsa-bill]

Helicoils from http://www.uni-thread.com/ in UK, I've used them before, also the inserts come in differing lengths so I bought some longer than the stock 1.5 times width.
I've also noticed the drills that come with the kits are not your usual size - for instance I have one that is 9.8 mm, not sure if that equates to an imperial size or not but could be as all the kits I've bought are for BSF,Whitworth or cycle

Got the holes drilled out ready to tap for the inserts; all bar one look to be pretty well drilled to vertical, might just be a suggestion one has a bit of bright metal on one side at the bottom of the hole.
Got two holes tapped for inserts before calling it a day, proving to be very difficult to get the tap started square to the hole, can't trust my eyes these days something happens between my eyes and my brains interpretation of what I think I see, I keep checking with a small try square, tomorrow I'll be away most of the day but I must find something to feed the tap through that keeps it square to the barrel, thinking along the lines of a box spanner or similar.

[muskrat]

Thanks Marcus. All my kits are recoil, I'll have to ask my local supplier.
Bill, I use the tap in the drill press to get started square.
Cheers