Hi David,

the thread is 1/2" BSCyc with 20 tpi definitely. I have just gone through the exercise having to properly cut the thread is a pattern part nut 24-7000 as it would not catch the thread on the camshaft.

As BSCyc and UNF share the same thread angle of 60° I took a 1/2" UNF tap

I hope this helps.

Cheers!

Ph.


Best regards
Phil
Duesseldorf/Germany
'62 A 65 Star (disassembled)
'69 A 65 Lightning
'71 A 65 Firebird
'84 Yamaha SR 500