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1942 WM20 speedo drive.

I have searched on this topic and have not found what I need.
I am having trouble fitting my speedo drive into the forks, the drive will not clear the forks.
I have assembled the front axle exactly as shown in the front axle diagram.
The only internal part I am not sure of is part No. 24-6867, I have 2 different lengths for this part. When I bought this as a basket case I suspect there were some B31/B32 bits in there, this may explain the 2 differing axle adjusting sleeves, don't know if this would have any effect on speedo drive fitting. Also, I know that post war drive is thicker (?) than 1942 version, how can I check this. (possible that my drive is B31/32 ?) It has the correct rotation.

Any info greatly appreciated.

Baz

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Baz, I just measured up a used 24-6867 as 0.590" thick. The locknut 24-898 is 0.191".

The washer 66-5524 that sits in the recess inside the speedo drive is 0.078" thick (that was a note I have in my parts list that came from a discussion on this forum years ago so passed down info I guess. (I machined a spacer this thick for my bike and it fits perfectly BTW).
I recall in the same discussion it was mentioned that one of the two big washers on the outside of the speedo drive (36-3528) could be removed if required but I am hazy on the specifics - someone else may know this one.

email (option): rays54@hotmail.com

Re: 1942 WM20 speedo drive.

:+1:

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

I'm not well up on post war models, but did a B31/2 have such a speedo drive? I thought they were driven from the gearbox? Other tele fork makes that were driven off the rear wheel where generally driven from the right side and therefore the wrong rotation. To double check the rotation for a girder M20:- Turn the drive dogs clockwise and the cable drive should also turn clockwise.....Most you see are the wrong rotation.

Have you perhaps got the earlier forks that weren't splayed out on the left for the speedo drive?? Ron
Scan-140318-0001

email (option): ronpier@talk21.com

Re: 1942 WM20 speedo drive.

The speedo rotation is correct Ron. I don't know about the splayed forks I have not noticed a difference between sides, I have 2 sets and will check tomorrow. (100deg here,too hot !)

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Ron,
Neither of my forks, one of which came originally with the bike, are splayed.
Where does that leave me with fitting a speedo drive ?
Baz

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Baz it would be a rare coincidence to have two pairs of early KM20 forks which were fitted with an angle speedo drive through the brake plate.

I'd want to identify your forks first. The scan above shows the standard later longer forks which measure 17 1/8" from the center of the damper spindle to the center wheel spindle and would need the 1/2" hex spacer at the central mudguard support.

The earlier "splayed" forks were 1/2" shorter ie 16 5/8" between the spindles.

To measure the distance between the wheel spindle ends:- Draw a straight line on a board, lay the fork so the line passes through the center of the top grease nipple and the mudguard support and measure from the line each side, the left side should be 1/2" wider.

If indeed you have got KM20 forks? I would offer them as a swap to someone who actually needs them. But if you have WM20 forks that someone has wound in to fit a wheel without the speedo drive, then you would have to clamp them down somehow and bend each leg out to the required measurement.....I've done it on about four occasions to bent forks. When the forks are bent backwards it's a whole new kettle of fish:thinking_face:

Some picture of what you have would be handy. Ron

M20-132

email (option): ronpier@talk21.com

Re: 1942 WM20 speedo drive.

Thanks Ron, looks like I have a lot do do. At the moment, temps are close to 100 deg everyday (36C today) and hotter in my metal shed, so I am limited in time I can spend. Hoping for cooler weather soon!
My other, easier option is to check another 4 sets of forks I have access to and see if one of them is properly splayed.
I can take some pics and send them to your email if that is Ok.
Thanks again.
Baz

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Ron, did a bit while still coolish.
Both forks are 17 1/8"
Using your method to measure, spare forks are splayed on LEFT side 1/2" (3" and 2.5")
Forks on bike are 2 19/32" on Right side and 2 13/32" on left. Looks like bike forks are squashed in 11/16"on left.
Can't post pics here, I'll send them to your email.
Baz

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Here are your forks Baz. They must have got squished sometime. If you can hold them somehow, you can bend the legs outward with a long bar and no heat required.

My vice is big enough to hold them between the damper plates and I have a 6' crowbar and with enough pull to overcome the spring back, I've done it with no problem. Or some 13mm studding with nuts on the inside of the legs, clamp the studding in the middle and wind each nut out to the required distance. Again you will have to overcome the natural spring back.....But you are lucky to have six forks to choose from. Ron
Baz
Baz-2

email (option): ronpier@talk21.com

Re: 1942 WM20 speedo drive.

Cheers Ron, I'll have stab at bending them.
My club has all the spares and my deal was to buy a basket case, with any spares required to complete it at no further cost.
Very hot day and I couldn't be bothered to drive over there.
Next opportunity will be next Monday, if the bending doesn't work.
Baz

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Well it looks like your spare forks need to go out an even 3/32" both sides and your first forks need the left side to go out about 11/16". It's the sort of thing that warms us up on a freezing February morning here in UK:snowflake:

Ron

email (option): ronpier@talk21.com

Re: 1942 WM20 speedo drive.

I would make a jig in steel to hold them square before even thinking about bending them. I have the same task to tackle, but it will be a while before I'm allowed the time to do it.

email (option): pes.sales@btconnect.com

Re: 1942 WM20 speedo drive.

Baz Ford
Cheers Ron, I'll have stab at bending them.
My club has all the spares and my deal was to buy a basket case, with any spares required to complete it at no further cost.
Very hot day and I couldn't be bothered to drive over there.
Next opportunity will be next Monday, if the bending doesn't work.
Baz
Just an update Ron. I used the threaded rod method. No luck until I used gentle heat in the right spot.
I gave up on the worst forks and got the others to within 1/16" overall. Works a treat now.
Thanks again.
Baz

email (option): binnawan@iinet.net.au

Re: 1942 WM20 speedo drive.

Good to hear Baz. The sideways bend on the parallel tubes each side is relatively easy to adjust. Like the back end of an M20 frame that are often out of line, can be straightened cold with a long bar, as long as you can hold the frame. I know one guy who had a perfect crook in an apple tree to hold his frame.

One pair of forks that were presented to me by a friend who ran into a car that pulled out in front of him were bent backwards by an inch or more. They beat me, but fortunately I have an excellent tube firm nearby who straightened them. Ron

email (option): ronpier@talk21.com

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