[iansoady]

 Success!

Held the valve in the 4-jaw with the head behind the jaws and cleaned up the groove with a Dremel in the toolpost & a fine grinding wheel. It took very little to restore it to round and cylindrical.

I was scratching my head trying to work out how to establish the outer taper on the collets and then to cut it. The former I achieved by filling the collet  with Plasticine then measuring that as the internal dimensions were tricky to measure accurately.

Then set up an old HT bolt in the 3 jaw chuck and used the compound slide to set the angle. Did this by setting the cross slide to zero at the end of the blank with the tool touching the blank, then winding the compound slide along till the length was correct and using the cross slide to wind in the tool till it touched again. I could then read off the lateral distance.

I thought that would be much more accurate than using a protractor.

Then turned the taper, drilled (6mm, the new diameter of the recess in the valve), parted off then sawed the resulting part longitudinally on opposite sides. Cleaned up and it fits very well.

It wasn't as hard as I thought it might be.

[iansoady]

Yes John, the parts book shows them as being common but the included angle in the exhaust item is definitely different. I'll just make the collets to fit. The retaining collars do look superficially identical.

[singleminded]

I think that the 12 deg is correct..
I have to make collets for my M90 engine at some time. I tend to adjust the topslide till I get the taper to fit the top collar and my 10 deg was off the top of my head.
Someone most likely has adapted the wrong top collar to fit with the nearest collets available of were made to fit the wrong collar.
My spares book for the M10 etc shows the same part no for the overhead collars, inlet and exhaust. John

[iansoady]

Thanks John.

The plot thickens....

Close inspection of the valve showed it was a bit mashed up where the collet fits so I've trued that by using a Dremel with fine grinding wheel in the lathe toolpost and the valve in the 4 jaw chuck. But I've also discovered that the taper in the spring retaining cup is different between the inlet and exhaust valves - inlet is around 12 degrees included angle; exhaust (the one I'm working on) 18 degrees. I thought it was my measurements at first but when I put the inlet valve & collets into the exhaust retaining cup it wobbles about whereas in its own cup it's quite firm.

So now (after measuring twice more) to make some collets out of an old HT bolt.

[singleminded]

Yes.It looks like the outside taper is the same as the M9 but the inside looks parallel, unlike the M9 etc that has internal and external taper.
The taper appears to be about 10 degrees..john

[iansoady]

Yes indeed. The funny thing was it fell out when the head was just on the bench, not when I was compressing the spring.

It has struck me that maybe there was only one in there in the first place which would perhaps explain it, although it waited a few seconds before it all sprang apart.

You haven't seen the state of my garage floor otherwise you wouldn't suggest the magnet. You could hide a Sherman Tank in some of the nooks & crannies.

I've just reread Radco's book and think I'll try to make some new ones....

[singleminded]

It's a right beggar when that happens..
Best bit is though, if the collect fell out on the bench what would the outcome have been if it had fallen out when you were riding?
I had a similar problem and what I did,couldn't see for looking. I got a magnet and swept the floor with it and under the benches and eventually found the bit..john

[iansoady]

I just wanted to check the compression ratio on my Model 10 so had the head complete with valves upside down on the bench. I heard a tinkle and there was one of the exhaust valve collets lying there. I wasn't quick enough to stop the other one shooting across the workshop and of course it's vanished.

Just in the hope (a) that it's shared with another model and (b) that someone has one lying about its dimensions are:

Length:  0.463"
Bore:     0.250"
Major diameter:  0.600"
Minor diameter:  0.412"

My parts list suggests that this part is, like so many other, unique to the model but I can live in hope.

Otherwise I'll have to try to make one and I'm not sure my machining skills are up to it.......

I have to say it's a good job this happened on the bench not when the engine was running.