Turning road bike into trials dirt bike…
My first trials dirt bike was born circa 1963, although the manufacturer had never intended this particular model to become a trials motorcycle. It was in fact, a 250 cc Greeves, powered by a twin cylinder Villiers 2T engine that was fairly quick in it’s day, although it had to be coaxed back into life on a monotonous basis because the wretched thing would stop working for a past time.
A little bit of dirt bike history
The Greeves Motorcycle Company was a small engineering firm that was based in Thundersley, Essex in the UK and was run by a couple of guys by the names of Bert Greeves and Derry Preston-Cobb. The company manufactured road bikes (my model), and a range of world beating motocross and trials dirt bikes, both of which had enjoyed a fair degree of success back in the 1960s .
Anyway, back to the story.
The reason for thinking that my bike could be the doner for a trials dirt bike was born out from the fact that all of the models built at Thundersley employed an aluminium casting instead of the usual tubular steel downtube that usualy formed the front of the frame that houses the headstock at the top, and engine mounts at the bottom. OK good enough for me. First job, out with the hacksaw and off with any bit of metal that was superfluous to the cause, (very soon there seemed to be a bigger pile of scrap than frame now), what next, ah, lights! this was way back in 1966 when a trials dirt bike didn’t require lights to be fitted as long as it was only used during daylight hours, before the street lights came on, duuuh. So off with the lights and any bits of wire that wasn’t being used for something important like a horn. Oh, horn! don’ t need that, off it comes, an exhaust/silencer system that probably weighed 50% of the total bike weight on it’s own, and so on. Right, so what have we ended up with. A much lighter twin cylinder machine with repositioned foot-pegs and leading link forks, you know the type, they had a lump of rubber in torsion controlled by a couple of small dampers and when you applied the front brake the front end would rise up as opposed to dipping like a conventional fork. The bike still had it’s original dual seat with aluminium mudgaurds and a couple of flexy pipes for the exhaust. SO! The big day, off to my local piece of scrub land down by the stream to put it through it’s paces. “So, how was your dirt bike” I hear you cry? Crap, was the reply!
It takes a bit more imagination to create a good dirt bike
What I needed here was a bit of a re-think. Clearly the engine had to go along with the front forks and I still needed to loose a couple more pounds in weight. I decided to remove two large slabs of steel from the humungus engine plates that ran beneath the engine from the “downtube” to the middle section of the frame, when all said and done, these were only really there to house the original footrests and centre-stand as the engine itself was a stressed part of the construction. The real plus point was that I actualy gained about 2″ extra ground clearance. Another huge weight saver was the purchase of a genuine Greeves Challenger motocross fibreglass tank in favour of the all-steel road version that was also much wider. At this point, a club-mate said he had a Villiers 225 cc engine that came with a carb and a modified motocross exhaust system that would bolt right into the frame as the bolt hole centres were identical to the twin engine, we did some sort of a deal with PX and cash and off I went to bolt in my new motor.
Next, the forks. Not far from home was a motorcycle breaker who sold me a pair of telescopic forks that started life bolted on to a 500 cc Ariel road bike of 1940/50 vintage he then said ” If you need head-stock bearings to marry these forks to your frame you will need to check out some boxes. In this box we have different cups, in this box different cones and in these boxes different size ball-bearings, match them up and you can have the lot in with the price of the forks” Thanks! I also bought a 19″ half width hub wheel and rushed off home to bolt it all together. The next thing to buy was a single trials seat which you could get, you know the sort of thing, one size fits every dirt bike.
At this point, believe it or not, my trusty steed actually started to look a bit like a trials dirt bike the other guys were riding.
I rode quite a few events on this modified beauty and found that it wasn’t a bad ride, by no means perfect, but ok. I mean, the majority of blokes riding stuff that was specificaly designed and had been built as a pukka trials dirt bike, usually cost a lot more money to buy whereas, I was trying to build a competative hybrid on a shoe string budget.
Finished? NO, the metamorphosis was not yet complete. See what happens to the old Greeves in the next installment…….
The Dirt Bike Rocks.