AJS & Matchless Owners Club

It's time to turn back to the engine as I've been waiting for other parts. Upon closer inspection the crank pin is worn. At first it was thought to be the bronze bush ( oil pump ) side. Can the crank pin be replaced and is it a machine shop job or would i be able to do it with advice?
I'm sure it will suffer from a few problems,low oil pressure being one. Any advice on this would be greatly appreciated.
Regards Roger.

The pins are available from the club, I got my G5 one from Alpha on exchange.
You can do it yourself if you have the means. Beside pressing them together you'd need to put the crank between centers to clock true the flywheels.

Martin.S wrote:The pins are available from the club, I got my G5 one from Alpha on exchange.
You can do it yourself if you have the means. Beside pressing them together you'd need to put the crank between centers to clock true the flywheels.

I have the access to a press and a lathe.....Not that Im any good on a lathe.
Will look at the parts list now
Who is Alpha if you don't mind me asking?
Cheers Roger

Parts list for Bush is out of stock and couldn't find the crank pin

If you're just changing the pin, you need the bigger diameter 350 one for your bike.
http://www.amoc-parts.com/store/comersu ... duct=22362

I got a complete exchange con rod and big end from Alpha, which made the job easier.
http://www.alpha-bearings.com/Big%20end ... 250350.htm

clanger9 wrote:If you're just changing the pin, you need the bigger diameter 350 one for your bike.
http://www.amoc-parts.com/store/comersu ... duct=22362

I got a complete exchange con rod and big end from Alpha, which made the job easier.
http://www.alpha-bearings.com/Big%20end ... 250350.htm

Thanks for the links.
It seems to be a money pit but have to finish it.
Can you give me an idea of the second cost please.

It looks like I paid £220 for a new pin/bearing and exchange conrod from Alpha.

Martin.S wrote:It looks like I paid £220 for a new pin/bearing and exchange conrod from Alpha.

Thank you for that. It is reasonable based on what you get Roger.

An update since last post.
After weighing up my options I managed to find a local engineering guy who repaired the crank pin as there weren't any available. Also the main bronze bearing was also unavailable so I made one myself. As of now the crank is back together and after hours of head scratching it is true.
The other reason for posting is there doesn't seem to be any clear drawings of the 250csr engine rebuild.
Can anyone point me in the right direction or put up a link as I do not want to miss anything before closing the crank cases. All help is greatly appreciated.
Roger.

There are no clear drawings that I'm aware of

The only bit that isn't obvious is the main bearing arrangement. I made this diagram to try and show it: Most important check is a minimum crank endfloat .040" without the sprocket fitted. This endfloat will fall to zero once the sprocket is fitted.
Also, make sure the sprocket is fitted the right way around. The right way looks wrong.
http://www.jampot.com/forum/viewtopic.php?f=15&t=17322

Good luck!

clanger9 wrote:There are no clear drawings that I'm aware of

The only bit that isn't obvious is the main bearing arrangement. I made this diagram to try and show it:

lightweight_main_bearings.png

Most important check is a minimum crank endfloat .040" without the sprocket fitted. This endfloat will fall to zero once the sprocket is fitted.
Also, make sure the sprocket is fitted the right way around. The right way looks wrong.
http://www.jampot.com/forum/viewtopic.php?f=15&t=17322

Good luck!

That is one of your sketches I have come across in the past.
I may be missing something here but how is the 40thou end float measured when it is encapsulated within the crank case.
As I see it the crank mains will not move once bolted up and therefore is the end float measured from the inside of the sprocket?
The how to's are limited even with the Matchless manual. It explains in detail about everything else apart from the bottom half
Thanks once again for the info
Roger
PS missed your Link