1929 Model 19

I don't Know much about Early Norton singles,but my thirties Rudge has 2 compression rings only on a modern Gold Star piston. Rudge barrels are usually set up with 7 or 8 thou clearance to avoid seizing and use a direct oil feed to the barrel .Some still seize. Rudge cylinders change shape once heated and early alloy pistons had a high expansion rate. With early technology its best to follow established practise otherwise it could be a slow and expensive learning curve. Total loss systems have to get rid of the oil so minor leaks and a smoke haze is the norm.

Previously Andrew Jarrett wrote:

Hi,

I am rebuilding a 1929 model 19 motor which is a total loss oil system and have found a piston that will suit after machining, but after a conversation with a friend he told me that the early motors only had 2 rings the piston I have has 3 rings which is what I consider normal.

Can someone confirm if they have only 2 rings and if so is it 2 compression rings only with no oil ring or 1 compression 1 oil.

I purchased this bike from an aquantiance knowing that he had problems with the bike siezing, I have found that the Conrod was 2-3 mm out of centre and a few other little issues.

If this engine is only meant to have 2 rings I will leave the oil ring out but would also like to know why the 3rd oil ring is not used.

Cheers

Andy

Good evening Andrew.

I don't have a model 19 but have a 1929 model 18.

I have run it for thousands of miles over the last 10 years but last summer I destroyed the piston returning from the Wicklow rally.

I was fortunate to locate a new old stock piston and had the barrel rebored to suit. (Incidentally both the original piston and the replacement have 3 compression rings and no oil ring).

I had the barrel bored 4thou oversize and it seized after 2 slow miles, I had it honed out another 2thou and it went for about 5 miles before seizing. I opened it up to 8 thou and it will run for 10's of miles but does nip up if I try a long steep fast hill. So now I'be taken an additional 2 thou out making the clearance 10 thou but have not had a opportunity to try a fast uphill run in hot weather. It does rattle when started before it gets hot but I don't mind.

Its clear that these early pistons were made of a high expansion rate aluminium. Try measuring the diameter at room temp the immersing in boiling water and measuring the expansion. I was surprised when mine increased by 9 thou with an increase of temperature of just 80 deg. C

Good luck

Jeff Read

I think what we are telling you (in a round about way!) is that what works ,and is established practise with modern engines does not apply to early stuff . follow the lead of others who have trod this path already.Do your research ,Castor oil and regular de-cokes could be your future.