Hello and building a G3 scrambler questions

[chamber66]

Hi
I'm new to this forum and to classic bikes, so a little out of my depth here.
i do a bit of twinshock racing, and have been thinking of building a pre65 scrambler. My dad is a Matchless fan, so it makes sense to buid one that we can both work on. Anyway couple of questions if I may. Can the late 50's G3 350 be made competative, using it's existing single downtube frame?
Also can it be converted to a 500cc, i have read that they can as long as you use similar years components is this correct?
, . I know it would be easier to buy a G80, but i know of a 350 locally.OR, I have seen these on E,bay and was wondering if they fit

http://www.ebay.co.uk/itm/Matchless-G80 ... _326wt_776

Thanks again in advance

[dave16mct]

I don't know much about MX but I would think you'd have no chance with a long stroke G3ls. You need a short stroke G80CS (perhaps in a Metisse frame). That alloy barrell will only fit comp crankcases or you would have to weld and move the through studs. Dave.

[Cjay59_LAPSED]

Is this of any interest, this book is sometimes hard to follow,


Classic British Scramblers - Don Morley 1986.

Wyatt and his men did not stand still; back in 1947 they had built a special one-off roadracer, known as the Cadwell machine, and it was to this engine that they next turned their attention (1951).

Roadracer Les Graham had smashed even the works camshaft Vellocettes and Nortons on this standard looking bike, the Cadwell being basically a one-off short-stroke, though pushrod engined prototype G50.

However, instead of building what was intended as a grown-up 500cc roadracing 7R, AMC elected in a change of policy, to tune the G9 twin.

Wyatt decided first of all to experiment with those somewhat wild Cadwell cams and recalls some of the problems; "We were having a race to see how the Cadwell cammed scrambler would come off the megga at low revs compared to the others, but, as I expected, it just wouldn't accelerate out of a hairpin, too much valve overlap and in any case it was a hell of a job to start. It was so erratic I even thought the magneto was up the stick and changed it, but that didn't help so I said, change the exhaust cam over to a standard scrambler one. When we did that the bike started in half a kick and it was so fast, it flew".

Further tests on this highly unusual cam combination established that the works machines were just as fast and even more flexible if given both a matching reduction in overall compression ratio, and an exhaust pipe and inlet manifold extension. Henceforth the works 350 and 500 long-strokes ran on a compression ratio's of 6.31 and 5.9:1, respectively, with their inlet valves now opening at 60 degrees BTDC and exhaust commencing 74 degrees BBDC.

Using a 500cc works Matchless in 1952, August Mingels finished second in the first Scrambles Championships of Europe, Malcolm Cox was fourth and Stonebridge sixth, whilst at home Reg Pilling came second and Stonebridge ninth in the ACU Star.

This then was the bike offered to the public in 1952 and continued in production until the end of 1955. Valve sizes on the 350 were now virtually the same as on the roadracing 7R, and on the 500s were not much larger. Carburettor sizes were 11/16in and 13/16in respectively wereas the Cadwell derived, HL stamped scrambles cams had also required the same valve guide and machining operation as on the 1948 Clubman TT machines.

Gear ratios remained exactly the same as the roadster counterparts, with ninterchangeable engine sprockets available from 15 to 21 teeth.

By this time AMC had won the four year old British Championships three times, and the works machines had travelled even further down the Cadwell road, by adopting it's short-stroke dimensions at the end of 1953. Although indistinguishable in appearance the AMC production motorcycles remained long-stroke until November 1955. To match the HL cams, Amal's TT10 carburettor was adopted as a replacement for the pre-monobloc instrument.

Matchless Cadwell 001..jpg

The result of the Cadwell engine experiment was this potent looking short-stroke model, in this instance a 350. Note the enclosed pushrod tunnels, much needed dual seat, but heavier roadster full-width wheel hubs.

[chamber66]

Thanks thtat was really interesting

[Cjay59_LAPSED]

Couple of fun G3's,

G3L 1961.JPG

WDG3.jpg

[Stan Palmer]

Posted in wrong thread.
Stan

[mdt-son]

Morley's write up is inaccurate and unreliable. I can't even take this with a pinch of salt.

While the Cadwell engine was a 350 experimental bike made by the Comp Shop for 1947 and intended for short circuit racing, Morley starts talking about 7R, G45, short-stroke engines .... what a waffle!

-Knut