AJS 250 CSR questions from a newbie

[triumph thaiger]

Hello , my name is Maxim Jurgens . I live & work in Phuket , Thailand. I have recently made and aquired a 'barnfind", an AJS 250 CSR . I intend to do a 'light restoration" ( "patina" is hip these days) after which I will give the bike to my girlfriend for her birth day . Which is Sept 10 ,so there is some urgency.I already have a 1971 Triumph Bonnie and a BSA M20 . I am new to AJS/Matchless bikes. After purchase I cleaned out the fuel tank & carb, replenished the oils , put in a new battery, kicked her over ( very low compression) and fired her up . She ran . Smoked a lot though and was pretty gutless.
Also, after oiling up a new plug twice in ten minutes it was clear some work was lying ahead. Good thing is that with her came a + 20 ( JP ) piston ,so someone in the past knew that she was in for a rebore.
We've taken the head off and some questions already arise . I hope some of you can advise. I have the Neill manual and the red Matchless manual.
.

1 Engine nr is CSR 144842 .Can anyone tell me what year this is from ?

2 head has coil springs . it also has ,what I think is added by a previous owner , over each valve guide a tight fitting stainless tube in which there is a valve seal. Were valve seals ever fitted by the factory ?. If not are they a good idea, a bad idea or does it not matter ?

3 Under the barrel a plate of about 1 mm thick has been fitted, presumably to lower the compression. Is this a known mod with these bikes ? Given that there is no valve lifter and that it would be very nice if my girlfriend could actually start the bike herself ( she is neither tall, nor heavy, nor esspecially strong) the idea of lowering the compression ( std is 9.8 :1 , I think?) does not seem a bad idea ,even if at the expense of some top end power . Any advice/experience ?

Many thanks in advance for your help. Best regards from a very, very wet& rainy Phuket

Maxim Jurgens

[saltbox alf]

Hi Maxim, welcome to the forum. I think you do have a 64/65 engine. You will get a better idea by contacting the dating service on the jampot.com website.
The plate at bottom of barrel is to lower compression, perhaps the local fuel at the time it was done was of low octane.
It seems a rebore is a strong possibility.
Coil spring valves are correct, never seen shrouds with oil seals though, could be a good conversion!

There are some very knowedgable owners of light weights on the forum and I am sure they will be along soon.

Regards from a sunny/hot sud de France!

[Janet]

I can't help with your engine number as my lightweight is a 1964 Matchless G2. Its number starts with G2 CSR and then has a 5 digit number.

The 1965/66 models had coil springs. The earlier ones had hair springs.

I don't know why anyone would lower the compression on these bikes. Get it set up well and it starts very easily. It's the only bike I have that I'll happily start while wearing soft sandals. Before anyone says it, at 5 ft 4½ inches tall (1.64m) I'm not particularly short (although I have relatively short legs) and the aging process means I'm not overly strong, but I do have a lot of weight. The bike has a long kick-start lever and the hardest part is getting my foot high enough to reach it.

When you've got it properly sorted, your girlfriend will leave you behind if you're on the M20. They will even climb hills very well, too, but remember, it is still only a 250cc.

I hope she enjoys it. If not, I'm sure you will.

Just something to note before you run it. Keep the oils topped up, but always make sure the gearbox is up to it's correct level. THe moving parts are at the top, so a low oil level means they don't get proper lubrication, unlike in the engine where there is a pump to get it up.

As has been said, there are some very knowledgable owners of light weights on the forum and I am sure they will be along soon.

Regards from a sunny/hot Yorkshire, England.

[Rob Harknett]

Valve seals were fitted to side valve AJS way back in the 1920's. I doubt if they did much, they were nothing more than a flat washer and voile spring.

[Ozmadman]

The valve oil seals are a botch of some kind probably to stop it burning oil because of worn guides. These engines do not have or have ever had valve stem seals fitted. Take the stainless less junk off, check there is no play between the valve stems and guides and if there is then replace them! as for the plate at the barrel base, another botch for god knows what, take it off, and as Janet has said... set it up properly, points, timing etc and you should have no trouble starting it