Classic Dirt Bike

[Phil Hyde]

Issue 56, Autumn 2020 landed today.

A nice article on a 250 Challenger. Of particular interest was the detailed story line on the BSA gearbox contained within a casting one of a series made by Robin Humphries of REH.

How many of these were actually made? Perhaps our Challenger community would care to comment

[druid]

Phil,
I've never seen one of REH's conversions but I have seen a few home brewed versions. A bit surprising that it is fitted to an MX4 (1967) as by this time the Challenger had the 360 type gearbox which was a vast improvement on the the dreadful HJ5 1964 version. In fact the early Griffons used the same gears. The biggest problem was the selector mechanism which led to wear on the gear dogs, especially if not correctly assembled and maintained, the situation eased when the Griffon box arrived.

One side benefit of fitting the plunger A10 gearbox was that it gave you a splined shaft and the opportunity to fit a Norton clutch.
Most of these mods were fitted to MX1 and 2 Challengers, it usually meant that you had to settle for the BSA standard road ratios. Scrambles gear sets for this box were difficult to find in 1964 and the situation has only got worse.

Druid

[Phil Hyde]

Hi John

Good to hear from you. Nice to get some sensible feedback in these strange times.

If you have not seen the magazine I will scan the pages and mail them over, let me know. Classic Dirt Bike is no longer mainstream and like so many of Morton’s publications their days are numbered.

Stay safe

Phil