AJS & Matchless Owners Club

I had something like that happen to me back in the 50's when a teenager Clive. I only had the engine stripped for a decoke. The tubes appeared to me as a tight fit in new rubbers. The head had not seated. I thought then, if I tightened the head the tubes will go in. They did not. I noticed just a little too late, the tubes were starting to splay out at the bottom on the crank case. Since then I now always make sure tubes are first fitted on the bench, into the head.

I have just had a look at the flat top piston at TDC picture. With the flat Hepolite I would expect it to be flush with the top of the barrel not projecting. I wonder if you might have a barrel that needs a decompression plate, there was a period when they were fitted as standard I believe. Along with the tubes not going fully home that might explain the problem. Might be worth measuring the barrel.

Rob Harknett wrote:I had something like that happen to me back in the 50's when a teenager Clive. I only had the engine stripped for a decoke. The tubes appeared to me as a tight fit in new rubbers. The head had not seated. I thought then, if I tightened the head the tubes will go in. They did not. I noticed just a little too late, the tubes were starting to splay out at the bottom on the crank case. Since then I now always make sure tubes are first fitted on the bench, into the head.

Hey ho Rob how do you think I came up with the advice, been there done that!

clive wrote:I have just had a look at the flat top piston at TDC picture. With the flat Hepolite I would expect it to be flush with the top of the barrel not projecting. I wonder if you might have a barrel that needs a decompression plate, there was a period when they were fitted as standard I believe. Along with the tubes not going fully home that might explain the problem. Might be worth measuring the barrel.

There is a plate in the parts list, however, it says can be used with high comp piston to lower compression. Or something like that, It gives plate thickness, which is very thin. See parts list for exact details given and plate thickness.

Bike came as a box of bits Rob. No reason to assume the parts are correct for the year as you often comment. I have one barrel that has to be fitted with a plate that is approx the same size that the piston is projecting above the barrel. If not fitted the piston catches the valve. Admittedly the bottom flange looks different to Adam's. Will try photo later today.

Well I dug out the barrel.
The observant among you will see it has rear of the barrel cut away for fitment to a Matchless with the magneto behind the barrel. However this was a mod I carried out to a later barrrel when I had a 1949 G80. Sold it which is a shame really as its been relined and I have an original wirewound piston which fits.

Anyway on to fit of the pushrods tubes. This barrel measures 5 and 1/2 inches from the face of the flange where it mounts on the crankcase to the top of the uppermost fin. Another 500 barrel I have measures 5 11/16 across the same dimension. The spacer plate shown on the barrel is 3/16 which would make up the difference. I seem to remember the problem with pushrods tubes, they seemed were too long when I bolted it together without the spacer and the piston hit the valves.

Thank you so much for all the replies!

So i have measured the barrel and it is 5.5 inches so Clive i think will need to try and track down a compression plate like yours. I saw one on a popular auction site but it was only 70 thou thick which is not quite enough.

Failing that i will have to track down another barrel.

Thank you again, its good to know there may be options yet.

Regards Adam

Easy enough to make a compression plate and cheaper than a barrel.

adz25 wrote:Thank you so much for all the replies!

So i have measured the barrel and it is 5.5 inches so Clive i think will need to try and track down a compression plate like yours. I saw one on a popular auction site but it was only 70 thou thick which is not quite enough.

Failing that i will have to track down another barrel.

Thank you again, its good to know there may be options yet.

Regards Adam

Before you start to track down another barrel which may turn out to be another wrong bit. Can you confirm the engine is 1953. Also what is the part number cast on your barrel L/H side flange. Check your parts list, if the barrel you have is wrong, then the parts list will tell what barrel you need.

Rob, the cases are definatly 53. The barrel casting number is 013843 which does not appear in the 53 parts catalogue.

I will have a look in the previous years if i get a chance to try and decipher the year of the barrel.

Many thanks

Adam