Can anyone tell me the outside diameter of the upper and lower fork bushes on a WM20 please? I’m asking so I can work out if my bores have been sleeved, thanks.

email (option): timmykins@icloud.com

Upon further investigation, the bores in my forks and steering head are in the region of 0.620, give or take a couple of thou.
I believe they should be around 0.680 thou.
I’m wondering……..do KM20 forks have a smaller bore for the bushes? My bike has the earlier anti vibe handlebar clamps. Could it have been given earlier forks too….

email (option): timmykins@icloud.com

Hi mate,

I have sent you the measurements of a NOS bush via messenger.

email (option): bsawdm20website@gmail.com

Thanks Nick.
To further add to the mystery the bores on my steering head clamps and forks match the OD of B series fork bushes. But my forks look like M Series ones.

email (option): timmykins@icloud.com

Most of the telescopic forks used the same bush dimensions, stanchion diameters etc...The lower fork sliders varied in format to suit the different wheels employed on various models and years of manufacture..There were also steering yoke variations for different years but also used with the same stanchions...Very early B31s and later Gold Stars had slight differences...Ian

email (option): ian@wright52.plus.com

Telescopic forks? I thought he was talking about the bushings on a girder fork WM20?

Probably, I was thrown off by the reference to 'B Series' and didn't immediately think of pre war B Series...Post war B Series only had telescopic forks of course...Ian

email (option): ian@wright52.plus.com

I can see now where I've caused confusion. I meant B model bikes, with the lighter weight (solo rider) frames, WC 10's were also fitted with the same girder fork. Did KM20 forks have smaller OD bushes by any chance?
It's a mystery why my forks have smaller Bush orifices than a WM should!

Tim the C models didn't share the same forks as the B models. There were about a dozen models in the 1940 catalogue with a total of 8 different forks. The 1939 KM models shared the same fork bushes as the 1940 WM models.

Some pictures of your forks might help ID them.

Ron

email (option): ronpier@talk21.com

Here,hopefully,are photos of my forks. In the last one you should see where I've attempted to see if there is a sleeve in the bore, there really doesn't appear to be!






numbers remove duplicates

Here is a close up of the part no. stamped into the forks.

Tim I don't think those are WM20 forks. The hex hole on the left side is for holding an early two part spark plug to take it apart for cleaning. Which is usually a pre war thing. Ron

email (option): ronpier@talk21.com

Thanks Ron, the mystery begins to unravel!

email (option): timmykins@icloud.com

Also Tim. For a WM20, the left leg is splayed out to accommodate the speedo drive. The earlier WM20 forks were 1/2" shorter than this drawing.

Ron

email (option): ronpier@talk21.com

Thanks for the above info. Ron. It makes sense now, why I struggled to get the front wheel assembly in.
I asked Darren Cartwright and he almost immediately told me the forks I have are from a 1935 Blue Star. 1935 being the year they introduced the spark plus holder. I very much appreciate your help mate.

email (option): timmykins@icloud.com

I expect Darren is absolutely correct. I'm not well versed with the pre war stuff. Here is the 1935 brochure picture. Right side only unfortunately. £57....Outrageous! Ron

email (option): ronpier@talk21.com

These forks were also fitted to 1936 models with a 14mm spark plug like Empire Star, Blue Star etc. I may have a set of M20 forks. Mail me off forum.

email (option): leonhop3_at_planet_dot_nl

Hi Leon,

I have emailed you. I swopped the characters in your email address on here into a working address. If you don’t receive it, my email address is the same as the one I use on here.

email (option): timmykins@icloud.com