I think you're looking at it wrong. It's studs 40 with washer and nut 35 36. With different length studs for the pannier fitted bikes especially on the left side which also holds the chainguard and field stand clip plate.
The backstay to saddle tube is a bolt 66-4636 Which Drags list as UNF which can't be right. Originally it would have been 20 or 26 tpi BSC.
email (option): ronpier@talk21.com
Josh, the two lifting stay bottom studs are 5/16" x 26TPI Cycle thread.
The two listed here are the longer ones suitable for the pannier rack and long field stand.
The longer one of the two is for the left-hand side that has the extra bits.
The backstay bolt 66-4636 is 7/16" - parts book shot below ( I think the pre-war bikes had a stud here but I'm not sure of that).
I have a NOS one in a frame in the shed - I can check the TPI tomorrow.
email (option): rays54@hotmail.com
The drags picture is more of the civy option, which wont include the lower pannier support tubes as well as the other parts mentioned on the left side. If the threads in the frame are weak, (for those who can't or don't want to weld up the holes) you can use Set bolts through from the inside with maybe a dab of Loctite, but I think you can hold the heads with a spanner anyway. Ron
email (option): ronpier@talk21.com
Ray/Ron,
Cheers for the information along with the pictures.
Ray..If you could confirm the bolt TPI, width and length it would be appreciated. My 41 WM had been converted to a B33 500OHV and im in the process of restoring the bike and have a side valve engine that im building up to fit back into it. As it had the OHV engine it had a different headstay fitted, the backstay bolt nut is only hanging on by a few threads and is not correct, however this may be due to the different head stay..ill need to obtain the correct head stay for the side valve engine and see how it looks then, Another question, ive seen pics of M20's and its looks as though the headstay attaches to the right hand side of the frame at the backstay..is that correct?
Ron,
Cheers for that, the hex spacers located in your pictures, Prt No: 65-6794. Could you please confirm the hex size, i need to order some in some hex bar so that i can machine some up.
cheers for your help
Josh
email (option): johnsonjosh@icloud.com
Josh, this is a photo of a bolt fitted to a NOS spare frame I have.
It matches the parts list diagram - 7/16" x 4 3/16" and is 20TPI cycle thread. The original washer is a a double spring washer.
The head steady is on the right as you say - here is a picture of one if you want to cobble something up?
email (option): rays54@hotmail.com