A65 Gearbox Camplate

[Servodyne]

Hi all. Does anybody know which is the latest type on cam plate fitting to the OIF A65?
I have the stepped cam plate, but it is too narrow for the slot in my end cover and wags about a bit. It's as if I need a none stepped cam plate or an end cover with a narrower slot.
My bike is a 1971 Firebird, so is the cam plate correct for my bike or my end cover and what was the purpose of the step in the first place?
Thanks all

[JulianS]

As far as I know there were 3 types - early with a boss (68 3187) - next with a step (57 2767),  then finally a thicker one without step or boss (57 4026) which used a different bearing plate to suit it for 1970 on.

[AWJDThumper]

I assume the purpose of the step is simply to provide a thicker and stronger bearing surface for the selector fork rollers. What is the actual width of the slot in the end cover? I believe the later cam plates were 3/16" thick at the bearing.

[JulianS]

Below is the Parts Bulletin from 1969 showing the change in part numbers but not (as usual) explaining the reason for the change.

[Servodyne]

I assume the purpose of the step is simply to provide a thicker and stronger bearing surface for the selector fork rollers. What is the actual width of the slot in the end cover? I believe the later cam plates were 3/16" thick at the bearing.

The slot in the end cover is around 5mm or 3/16" which is the same as the thicker part of the stepped cam plate, so it makes you wonder why BSA bothered with the added expense of machining the step when a wider slot would do the same job!

Thanks everybody. It's now clear that I need a new cam plate to match the end cover. Now does anybody know where I can find a reverse non stepped cam plate, so the shift pattern matches my A10 and Norton?

[AWJDThumper]

I believe the history of the A65 cam plate was as follows:

1962-65 (68-3043): used a strap across the selector fork slots to strengthen it

1966-69 (68-3187): used a step for the selector slots to strengthen it

1969 (57-2767): interim thicker (3/16") cam plate throughout for strength

1970+ (57-4026): final thicker (3/16") cam plate throughout for strength

[Mike Farmer]

 
Forgive my iggerance. Are they interchangeable.

Mike

[AWJDThumper]

No. The first two have a boss on the cam plate to fit a wider slot in the bearing plate, whereas, the later two don't have the boss but use a bearing plate with a 3/16" slot .

[JulianS]

See factory issued parts bulletin above - 57 2767 is a replacement for 68 3187 so the middle 2 interchange, the gearbox bearing plate being the same part.

[AWJDThumper]

I don't think it is entirely clear how the interim cam plate (57-2767) fitted with the earlier bearing plate design. From what I can tell, this cam plate was 3/16" thick and so wouldn't have fitted through the 1/8" slot in these earlier bearing plates unless the bearing plate for the late 1969 A65's was suitably modified; ie the slot was milled out to 3/16" width.

[JulianS]

Perhaps this link to a photo of a new old stock 57 2767 will help. It is stepped not uniform thickness;

http://www.klempfsbritishparts.com/CAMPLATE--A65--66-9--SHAVED-0

And this is the later plate 57 4026;

http://www.klempfsbritishparts.com/CAMPLATE--A65--70-72--LATE-0

The 1970 BSA master price list published by BSA shows the earlier 68 3187 as "Use 57 2767" so it supercedes the earlier part.

[Caulky]

My '71 spares book shows 57-4026 for all variants.

[AWJDThumper]

The cam plate 57-2767 looks like an interim solution and was only used for late 1969 A65's. It was superseded by 57-4026 in 1970. I think the first link below may not be 57-2767 but may be the earlier stepped 68-3187 - it certainly looks identical to it. The link indicates 66-9 which supports this. The advert I've seen for an interim 57-2767 actually says it will not fit the earlier cam plate because it is too thick. I'm assuming this cam plate is more or less the same as the final version 57-4026 with perhaps a tweak to the selector slot design??

However, there does seem to be a lot of confusion over which cam plate is which because there is no part number stamped on any of them. Since late 1969 A65's are a small fraction of the total, the earlier and later models can be more or less distinguished by the width of the bearing plate slot and the corresponding thickness of the cam plate at that end: earlier 1/8" and later ones 3/16".

[JulianS]

The 1966-68 camplate, 68 3187, had a spot welded brace over the selector slots, much like some Triumphs.

The best illustration is from the 1966-68 workshop manual which shows the braced item.