Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board BSA A65 Primary Cover

I’ve had good luck with the original post drive screws and copper washers from ace hardware. Got my set of four posidrive screwdrivers off the internets for not much. They have a hex at the top of the shaft that I can put a wrench on to get a screw out. Pays to have the right tools...when you see the screw head with the four scratchmarks at the 45’s

Hi, For my A65, I just obtained a replacement primary cover with the strobe opening. The bike, a 1968 Lightning A65, came with a substitute cover without the strobe cover.

Unfortunately, the primary cover it came with didn't have the level or drain screws. All other screws (Primary mount screws) are present. It seems all the primary cover screws are designed to mount the cover by going through the blind cover hole and screw into the case.

The drain and level screws merely screw into the primary cover threaded holes. Are the drain / level screws the same thickness and thread (Whitworth? BA?) as the primary cover screws? Just trying to get it set to start. If not, does anyone have the thickness and thread for the drain / level screw? TIA Steve

Pre-69 primary screws are 1/4 BSF.

Hi Steve, Which case do you have? A65's had the Alternator timing window from around 1967, but these early cases used 2 of the mounting screws for level and drain, so were pretty descrete (although prone to leaks). 1970-on had level and drain screws in an obvious position. Those cases use a course thread.

On the late cover with the "obvious" level and drain screw. The part number is: 14-7804 (google-ing the part number it shows as 1/4 UNC 3/4" length.

All the screws which go into your crank case though are as Nick says, I've heard Cycle thread also for these, when I look at Burton Bike Bits catalogue it states both.... But if its any help, On the case threads I helicoiled, these are 1/4BSF and they take the screws fine.

Thanks very much for all the information.

Allan, as far as whether my Primary Cover (with timing cover) is early or late, I don't know. It was purchased as a replacement for the primary cover on the bike lacking a timing cover.

However, your comment: "....but these early cases used 2 of the mounting screws for level and drain, so were pretty descrete (although prone to leaks). 1970-on had level and drain screws in an obvious position. Those cases use a course thread."

Soooo, I took a close look at my Primary Cover and removed a mounting screw. Sure enough the screw doesn't thread into the drain and level holes.

The Primary Cover does have a number on the inside, probably the manufacturer's number: 71-1045. Don't know with certainty if it is an early or late cover. But my guess, based on your helpful insight, is it is a later model cover with the "obvious" drain screws and corse threads.

Sounds like an early cover.
I didn’t find any difference in threads for drain and level screws although they were painted red at the factory.

To clear the chain?

Here is a discussion regarding level and drain on the 67/68 cover: https://www.britbike.com/forums/ubbthreads.php/topics/795310/67-68-bsa-primary-cover

And a discussion regarding the later covers with the separate level/drain screws: https://www.britbike.com/forums/ubbthreads.php/topics/840982/a65-primary-chaincase

Unfortunately, one conversation only shows the inside of the cover while the other only shows the outside, but it should be enough to understand the differences.

I hope I'm not beating this to death, but it seems we're going round and round on this early vs. late cover issue. Ok, up through 1966 the cover did not have an inspection cover over the alternator rotor. Up through (1969 according to a previous reply), the cover did not have separate drain and level screws. That is, the drain and level screws were the bottom two mounting screws. The later cover with the separate drain and level screws is immediately identifiable, as those screws are not at the edge of the cover.

The five screw posts around the chainwheel have that (orange circle) cutaway to clear the chain. If you run with a loose or worn chain those flats will have chain marks on them.
The screw post to the left in the picture is the permanent leak screw also known as the primary drain screw. The next one to the left is the level screw. Also a permanent leak screw. These screws need a fibre washer under the head (preferably with sealer) and the cover spot face cannot be worn or distorted. Otherwise they become a permanent leak.