Forum

[steverat]

Hello Gents,

Can anyone help me with the vital dimensions for a 500cc Bullet piston?
I confess - I need to know in order to decide whether I can use one in my AJS.

The diameter of a Bullet piston at +0.020" oversize is just right for my (already grossly overbored) old Ajay.
However, I need to know:
**Compression height**
**Gudgeon pin diameter**

Many thanks for your generous help
Steve

[Tim NZ]

Totally difference deck height: about the only other old brit single your could consider swapping a RE piston with would be the B33/34 BSA.

[simon]

A decent engine rebuilder should have a book that gives you the various piston sizes as a searchable list. My mate discovered that an Isuzu diesel light truck had a piston that suited his 1935 Panther 600.

[papasmurf]

steverat there are at least three suppliers of AJS pistons in Britain. It is going to cost you an arm and a leg wherever you get one from.

[Nettshubby]

Tim, he doesn't want to swap an Enfield piston, he wants to replace an AJS piston!

[Presto]

Why doesn’t someone answer the man’s question – instead of answering questions he never asked! The piston pin dia is ¾ inch and the distance from center of piston pin to top of piston crown is 52.5 mm – this is for the 38504A piston.

[Mark M]

Thanks Presto, my thought exactly, I was just off to find a piston to measure!

REgards, Mark

[steverat]

Thanks so much gents, particularly Presto for the precise dimensions.
The piston height is fine, crown is 4.6mm lower than the Ajay.
However the Ajay pin is 7/8" so I will have to think about that, means making up a new small end bush too.
An alternative would be to just use Enfield rings since I can get a piston albeit without rings.
Hitchcocks sent me some but they are 0.5mm deeper radially than the old Ajay originals - using them in an old Ajay piston would be asking for seizure I think.
Are there any +0.020" rings out there with a radial depth of about 2.5mm?
Best wishes
Steve

[Adrian]

Try a piston specialist! Here is just one, there are others. www.imdpistons.com . A.

[Bullet Whisperer]

Hi Steve,
I recently bought piston rings for a 350 AJS and a 650 Panther from these people, they will probably have what you need. Cheers, Paul.
http://www.classiccarwebsite.com/cox-turner-engineering