The Birth Of A Motocross Bike

The Francis-Bantam Motocross Bike ?    

Let me explain. When I was about 20 years old, I was competing in local trials events on my home brewed special, and had a brother who was 9 years younger who wanted to ride a motocross dirt bike. The problem was, as always, a dodgy cash-flow, so what to do!

This was back in the day when schoolboys rode converted BSA Bantams in local motocross events. One of the lads racing at the time was Neil Hudson who went on to become the 1977  250cc World Motocross Champion. Neil’s dad, Brian, had built him a bike using the celebrated Bantam, so if he could do it, so could we (me, that is)

Let the motocross bike build commence

I bought the bike and set about converting it. The first job was to work on the engine. A friend of mine had worked on making Bantam engines go a bit fastermotocross by machining two discs to fasten to the either side of the crankshaft flywheels to help speed up fuel/air mixture through the tiny transfer ports. On the outside of the cylinder barrel, he brazed a larger diameter inlet stub to accommodate a bigger carburetor, I think it was an Amal model. The engine was installed back into the frame that had whimpy front forks and a plunger rear end suspension system, if you don’t know what that is, ask your dad or better still, ask yer grandad.

We took a hacksaw to all the brackets and bits that were surplus to requirements along with the lights, excess wiring and stuff like that. The next thing was to build an expansion chamber exhaust system. As you might know, these are highly technical bits of equipment designed to get maximum performance from a motocross two stroke engine. OK, that’s all well and good, but all we had were a couple of lightweight conical tubes that originally served as  headlight bracket’s off an old 500cc Matchless along with some metal fork gators of the same diameter all welded together to the original header pipe. It kinda looked like a motocross expansion chamber even if it wasn’t scientifically correct. I’m not sure what we did about motocross tyres, I will ask my brother if he remembers, probably used the old road tyres.

This motocross bike needs further developement

My brother Tony tried out his (new) motocrosser. AND, rubbish! The chassis was just not sprung enough. I then had an idea, I knew of an old bike frame that had a proper swinging arm suspention. This bike had started life as Francis Barnett built in Coventry and powered by a small two stroke villiers engine. I aquired the frame, took it home and cut the front end off and binned it. Next, the back end of the Bantam got the same treatment, I then welded the two remaining bits together along with a couple of metal gussets making sure that the wheels and chain were inline and satisfying our dad that I wasn’t about to kill his youngest son (as if I would), made a new bracket for our trick exhaust, mounted the fuel tank and seat, and viola! our very own motocross bike.

Our Francis-Bantam had some strange traits. I recall taking Tony to a local meeting where he had trouble getting up a slight slippery hill, he was revving up and pushing hard with his feet but barely moving, so a couple of dads hopped over the ropes to assist, but still they struggled, it was then that I noticed  the rear wheel was actually revolving in reverse. What had happened, just before the hill, he had rolled momentarily backwards and the engine had caught and fired up in reverse, so these poor souls were trying to help him up the hill and Tony’s home-built racing machine was doing it’s level best to drive itself down the hill.

In reality, our Francis-Bantam motocross bike wasn’t that good, but it did give Tony a flavour of what was to come and he went on to ride in adult motocross  with some success for many years.

In the picture above, Tony and I are working on my Villiers powered Cotton trials bike, but you can just see the rear wheel of the celebrated Francis-Bantam motocross bike.

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