Tight timing chain on a Mark 3

Prior to the stripdown, was it running OK as far as vave clearance was concerned?

Do you know if the head or barrels ever been skimmed?

Are the pushrods the correct length, bearing in mind that if the head or barrel has been shaved, the pushrods should be shortened by the same amount to maintain geometery. This of course appertains to shavings by previous owners.

Apart from recessed valve seats (as Cash has mentioned) the only other measurement to check is the length of the valves themselves?

Without looking at the parts manual, I don't know if there is a measurement given for the barrels to determine the correct length?

Not much use, I know, but that's all I can think of.

I have owned the bike since 1981 when it was 4 years old. It was last running in 2001 and has been laid up in my garage ever since. I decided to strip it down and rebuild it with new parts at the start of 2008.

The head has not been skimmed and everything else is just standard Commando. The valve seats have not been cut. The only thing that did happen was that I took the cam followers out to get them refaced but I am sure that they are seated correctly. There is plenty of oil in the tunnel and with the head off I put the rods back in the tunnel and they were level with the pistons at TDC.

The adjusters are the factory fitted ones but even if they had been changed the problem is due to the rocker arm being too close to the valve stem. Hopefully if I can start it up then whatever is causing the problem may drop into place.

Colin,
Just "fishing" here, but do think it's possible that one of those tappet retaining plates (p/n 06-3092) is installed upside down? Could that restict the travel of the tappet, not allowing it go all the way down?

JimP, I think the retainer plate would affect both the intake and exhaust tappet, not just one valve as I understand Colin's problem.

Colin, not sure where you live but if you PM me I'll give you my mobile & you can call me, sometimes even going through it with someone on the phone can help, or maybe I can get someone close to you to help. Edinburgh club meeting next Monday, Tay Valley (Perth) 3rd Thursday if you need a roomfull of "experts!"

Thanks to everyone who has assisted with my problems on this forum.

Tonight I went out and put oil in the tank and started kicking the bike over to get some oil through the engine as I didn't like kicking it over too often with no oil flowing. After a few minutes of kicking there was a very loud "PING" and I noticed that the tight tappet was no longer tight!! I kept kicking and after a while stopped to try and adjust the tappets. Lo and behold the tight tappet had loads of adjustment and was able to be set as normal.

Definately a queer one as I had kicked the engine over quite a few times before tonight in an effort to see if that would clear the problem.

I am a member of the NOC and live in Glasgow. If there are any Norton owners around that area then I am hoping to set up another branch as there was 20 years ago.

I know that 'ping' ! I'd say without any doubt the pushrod was caught up on the edge of the cup on the follower. If you felt like pulling the top end off again, you'd probably see a small witness mark there.

Based on my experience, the push rods are probably springy enough not to suffer damage when this occurs. - Just be glad it didn't start !