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Forum picture bike

A nice example of a demobbed WM20 as the current forum picture bike. The American saddle must smooth things out a bit, but for me the limiting comfort factor is the clashing girders.

Re: Forum picture bike

A friend of mine has fitted a damper unit in place of the main fork spring...That could improve things quite a bit I'd have thought..The bike is currently being rebuilt but I'm looking forward to finding out how well the modification works...Ian

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

Re: Forum picture bike

That'd be interesting to see, Ian. Could you put it up here when the bike's together?
I think some Indians had a damper? And surely American chopperdom has produced something for the big twins.
And while on the subject of girders, do experienced riders rate check springs as an advantage?
I remember many years ago seeing a 1940s article in one of the British magazines about using rear stand springs as check springs on an M20. Don't know how practical this idea would be.

Re: Forum picture bike

Is that Jack?

Re: Forum picture bike

I'll post some pictures of the damper when the bike is a little more advanced....

I would say check springs are a distinct advantage...The M20 damper arrangement is a very poor design that doesn't even work as it should IMO...Apart from the fact its performance drops off very rapidly from being in an 'as new' state it also works in both directions, ie under compression as well as on rebound...

When it is tightened sufficiently to provide a [temporary] damping effect when the forks are on rebound, it also then acts on the fork spring when it is under compression. That effectively 'desensitises' the main fork spring to the light loads that are exerted by small irregularities in the road surface...
Another issue is that when the damper discs become worn and are not replaced and the damper hand wheel is simply tightened up some more in an attempt to restore the damping action, fracturing of the cranked fork damper plate is a common result...

I've frequently though of fitting check springs to my M20 even though they weren't a standard feature...Whilst I would argue for the M20 over other machines on a whole range of features, the girder forks wouldn't be one of them!!...Ian:relaxed:

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

Re: Forum picture bike

Ian Wright
A friend of mine has fitted a damper unit in place of the main fork spring...That could improve things quite a bit I'd have thought..The bike is currently being rebuilt but I'm looking forward to finding out how well the modification works...Ian
I recall seeing an M.20 in the 1970s with a damper unit installed instead of the spring and was told it worked well although I have never tried it myself.

Re: Forum picture bike

It seems to me that determining the correct rating for the damper may be a bit difficult and could present some problems....However, if (or once) the right damper is fitted I would have thought it would provide a clear improvement to the overall performance of the forks....

The bike in question isn't standard as it has a tuned 545cc ZB34 Gold Star engine fitted...The fork mods are an attempt to get the forks to keep up a bit better with the performance increase and to handle the improved braking provided by the 8" single sided BSA brake that's also fitted....Ian

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

Re: Forum picture bike

Yes, that's Jack.

Henk

email (option): ahum@quicknet.nl

Re: Forum picture bike

May I respectfully ask who Jack is? He looks a jolly fellow & I like his bike.

Re: Forum picture bike

Hi Bob,

Jack is guy from Holland and he is a dedicated BSA owner and user and also a very nice person.

Henk.

email (option): ahum@quicknet.nl

Re: Forum picture bike

I can't recall meeting Jack, but all the Dutch I've met so far are nice people. Ron

email (option): ronpier@talk21.com

Re: Forum picture bike

Thanks Henk

One of my best mates was a Dutch guy called Henk. We lost track over the years, as sometimes happens. Unfortunately he wasn't interested in motorcycles, but by God he could drink.

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