Back Street Heroes : 2020-09-01

SHED BUILT : 77 : 77


nearly twice as far, so there’d have to quite a lot of sums to arrive at what was actually going on). With that in mind, it’s not really surprising that a lot of ‘70s aftermarke­t forward control kits with a slinky little pedal that had, at best, a 3:1 ratio pulling (or worse, pushing) four-and-a-half feet of bendy ¼” rod didn’t do a very good job of working the back drum brake. Bearing in mind that a lot of American chops in the ‘70s ran without a front brake too, it’s all a bit scary. to use as well) between the bit you push with your foot and the bit that pushes the mastercyli­nder. Early motorcycle rear disc brakes were often added to a model that used to have a drum rear brake and, as such, often used the same brake pedal as the drum brake version. Once you get past the generation of Japanese bikes with their roots in the ‘70s though, you start to find rear brake pedals with something more akin to a 4:1 ratio. That’s a significan­t difference with almost half the of randomly sourced parts either doesn’t work or is unpleasant to use. Every time you use a spanner, that’s a lever working a screw, and everything with a bearing has rollers (albeit often ball-shaped rollers) so, while they might be ‘simple’ machines, it’s worth being familiar with the ins and outs of them if you’re going to build, or are even just interested in building, motorcycle­s. After all, it took some pretty bright people 1500 years to figure out how to use them to make motorcycle­s. 6 Not all handlebar levers have the same ratio either (Fig.5), which can lead to a clutch that’s heavy to operate or has very little (or just not enough) travel to free the plates. This same lever ratio problem is often the cause of poor rear brakes on trikes where the brakes are car-derived, and the pedal and master-cylinder are motorcycle-derived. It can also be the reason that an assemblage effort being applied to the master-cylinder, but because the master-cylinders have a smaller bore, the hydraulic pressure in the brake line is probably very similar, but as it’s not working a gargantuan twin piston ‘70s caliper the reduced volume of fluid isn’t a problem (although, if your foot’s moving through the same distance, the piston in the master-cylinder’s also moving 77 OCTOBER 2020