Turning road bike into trials dirt bike, continued
In the last instalment, my home grown trials dirt bike was converted from a Greeves roadster with a 225cc 2-stroke Villiers engine and Ariel telescopic forks.
The next major change to the bike came about because I acquired a 250cc BSA C15t 4-stroke engine with a broken gearbox, but with insufficient funds for the repair I managed to find a local bike dealer who was prepared to supply me with the replacement parts, in exchange for the 2-stroke engine, (who said the days of barter were over.)
The next job was to shoe-horn the BSA engine into the Greeves frame whilst keeping the gearbox sprocket on the new motor, in line with the existing rear wheel sprocket. This was achieved with more hack-sawing and grinding of the ever diminishing engine plates, (this trials dirt bike project was clearly not for the feint hearted), the lower engine cradle now acted as an integral bash plate to protect the sump. The interesting thing was that in spite of the taller 4-stroke engine, I managed to maintain, if not, slightly improve the ground clearance. There was an air / battery box in the centre of the frame, behind the original engine, which also doubled as a structural member of the chassis, so this was done away with and a bespoke oil tank was fabricated to take it’s place. There were other things to make, like an exhaust system, an air filter, a battery holder which was mounted behind a plate fixed to the fork legs, between the top and bottom yoke, and so on. The things that took the time building this trials dirt bike, were in the detail.
Trials dirt bike building – made easier with the right tools…
If I was in possession of my own welding gear, all of this would have been so much easier to do, however, the truth of the matter was that all of the mods required had to be mocked up and prefabricated before I could get to a friend of mine who had the welding equipment.
It was the little things that took the time, like cutting out fashioning a rear brake lever from a piece of duralumin plate to make a rear brake lever and connecting this to the hub via a cable.
Was my hybrid trials dirt bike any good?
This little trials dirt bike ran really well and was used in competitions for 3-4 years and was quite competitive in a world that was now being dominated by the new wave of Spanish marques.
After a time, I too was won over by the much lighter more powerful 2-stroke machines that was to drive the 4-stroke powered bikes into obscurity. The interesting thing is that now, the 4-stroke trials dirt bike are coming back to rule the roost.
When I think back on this project, I seem to recall that apart from a small selection of spanners, all I had for the fabrication was a hacksaw, a couple of files, one flat and one round, a DIY type electric drill with a few drill bits.
It’s surprising what you can achieve with a bit of vision, a few tools and a low budget.
Now, the project to build a trials dirt bike would have been so much easier if I had the right tool for the job.
We love the trials dirt bike