| Also known as | 40-740 |
| Diagram | Fig. 10 — CLUTCH AND PRIMARY COVER · ref 12 |
| Subsystem | engine bottom |
| Listed in parts books | 1969–1972 |
BSA Washer, for screw line 10 (alloy 17/64" × ⅜" × 1/16")
Alloy washer, 17/64 in. x 3/8 in. x 1/16 in., used under cover screws on the clutch, primary chaincase, and timing cover assemblies.
This is a small alloy washer, part number 40-0740 (also seen written as 40-740 in older books), that shows up under the screw line for several cover assemblies on the engine. In the parts books it's listed against the clutch and primary cover, the outer timing cover with kickstart and footchange gear, and the primary chaincase, so it's the kind of washer you'll find tucked under a screw head wherever those covers bolt down.
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It's sized at 17/64 in. bore by 3/8 in. outside diameter by 1/16 in. thick, and it's alloy rather than steel, which is typical for washers that sit against soft cases where you don't want a hard steel edge biting into the alloy casting. Catalog appearances run from 1969 to 1972, spread across seven listings tied to those cover and clutch figures.
It's a cheap item to have a few of on the bench when you're pulling covers apart, since these thin alloy washers are easy to lose track of or crush when covers get worked on repeatedly. Confirm exactly which screw position it goes under on your engine before ordering, since the same washer number turns up across several different cover figures.
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