Starting 1962 M21

[watts]

I recently bought a M21 which has been rebuilt from an elderly chap who had been woking on it for years.
I was not clear if it had run, I was not able to ask him, but his with thought so.

I cannot start it or even get any sign of life.

It is my first side valve and a bit lost now.

It has a new premier monoblock, refurb mag with a good spark when I turned it by hand on the bench. New points plug etc

New piston and rebore.

I cannot see the plug gets wet after kicking it for a while.

I also tried a new concentric that I had with similar result.

I have taken the head off and wonder if the exhaust valve us not seating properly see picture there also seems to a be a mark on the valve seat. I wondered about check the seal by spraying with some wd40?

Would this be enough not 'suck' fuel through.

Does the mag spark only on compression or on exhaust also?

I tried to time it with the head on, now it's off I will do it.

I could jut have timed on wrong stroke, but I think I got it right.

I would be grateful for any suggestions.

Thank you

Matthew

[iansoady]

The mag should only spark on the compression stroke as it runs at half engine speed. Can you feel compression when you turn it with the kickstart? That mark on the exhaust valve will lose compression but should still be enough to start. The surface of the barrel looks very rough and may not seal well.

[watts]

Hello iansoady

Good point.

I'll time it correctly with head off and should get some life do a compression test.

Then I might take it to an engineer friend who could mill it and the head, but Is that too much?

I have an engineers flat plate, I could try and do that with some grinding paste?

And reseat the valves.

Thank you

Matthew 

[maddogmargetts@yahoo.co.u]

the timing? There is a small nut on the top of the cylinder head on SV which you can use to measure the distance of the piston before top dead centre on the compression stroke. Should be 11mm on M21 engines. I use part of a spoke bent over so it does fall in. I mark it at TDC then wind the engine back to another mark which is 11mm away from the TDC mark. Alter the timing by removing the timing case cover, extracting the top gear which is the timing one on a taper, then the contact breaker is free to move to the 11mm BTDC using a fag paper to get the breaker as it just starts to open on that mark. Then put back the timing gear carefully so you dont disturb your adjustment. The other problem may be that the carb is worn out or blocked. Remove the main jet from the bottom and clean it. A new 376 amal from Buren in Cheltenham will solve a worn carb and at around £285 not a bad way to eliminate a possible fault.