1953 Model 18 AJS questions

dondlhmn · Post by **dondlhmn** » Sun Nov 30, 2008 2:19 am

I have my 1953 500CC model 18 torn down right now and have seen in some of the manuals that the compression can be raised into the 7:1 range by installing a later piston now that higher octane fuels are available than when the bike was built. I have several questions regarding this..(1) Has anyone on here done that? (2) Was it worth doing and does the bike produce more torque or horsepower? (3) How was reliability affected? (4) What piston for what bike has anyone on here used?

Secondly, the bike came from OZ and I was told that it did not need the air slide there. I think I want to put one back in for the sake of originality and, since it does get cool her in Reno, NV, I think I may actually need it. I know that some folk put a monoblock on, but I believe I would like to keep my pre-monblock and make it work. Comments/hints/help anyone/? If you have some input for me on either the piston or the car, I can be reached at dondlhmn@aol.com for email. I do also read the list often.

Oh…one more! I know the club has a spares scheme and I do intend to obtain some parts there, but what other sources have members found to be reliable/accurate and provide good parts for the AJS 18S?

itma · Post by **itma** » Sun Nov 30, 2008 11:33 am

hiccups Don?

jonesboy · Post by **jonesboy** » Thu Dec 04, 2008 7:59 pm

Hi,
The flat top piston is about 6.3/1 the later ones , ie 1956 on , with a slight dome give 7.3/1. These are the ones that seem to the most common supply at the moment. Beware of some of the ones marked ,heplex, as they are faulty if you look under the crown you will see this.
Yes going up an atmosphere in compresion will give the engine a noticable amount more torque.

wilko · Post by **wilko** » Thu Dec 04, 2008 10:18 pm

I thought i explained all this regarding the compression plate???