E DI T OR’ S S UMMARY

There have been some interesting trends in the results we’ve generated.

The clubman-equipped motors were all well below 20bhp, the highest of the nine on test was a 225 Lambretta running a Mugello cylinder and making 18.29bhp. Despite the limitation in power, the clubman often demonstrates a good ‘user-friendly’ power delivery and favourable riding characteristics. This particular result was on a super clubman being a few BHP up on previous clubmans.

The TS1/ RB /Monza type 225 kits in various setups but standard forms sit at around 20 to 23bhp as they arrive off the shelf, and power results vary with carb/pipe combos. Modified/long stroke/tuned 225 kits sat between 23bhp and 30bhp. These are common results on tuned 225cc reed-valve kits, and are typically fast-road setups. The final figure and rpm powerrange depends on pipe used and type of tune (porting job).

The tuned RB20 shows it can sit right there with the 225 and bigger motors in both power and torque as is the case these days with many of the available smaller kits especially when teamed up with a longer stroke crank to bolster the torque. These kits offer good value for the cheaper ‘small block’ casing option, and 30bhp is perfectly achievable with a 62mm crank, 34mm carb, Race pipe and a small amount of porting.

RB25 kits, when well-built, give reliable ‘off the shelf’ performance typically around 26-28bhp when fitted with the right crank/ carb/pipe combo. Mid 30s bhp figures are achievable, and still with stonking torque. 40bhp figures are becoming more commonplace on race machines when these kits are fully tuned and fitted with top-spec race components.

The new Casa 225 kit, when built well and set up with a 60mm stroke crank and Fran race exhaust did well at 29bhp. That’s probably the highest off the shelf 225 power figure at the moment. The bike engine machine category was split between 2 x two-strokes and 2 x four-strokes, and shows that nearly double the cc is required from a four-stroke to match the two-strokes peak performance figures, but just as is seen in the motocross world, the power width and spread from the bigger fourstroke motors is clearly superior.

The demo bike belonging to Eric shows how close that tuned Lambretta is to the power of a YZ250 motocross engine, and surprisingly showing the highest torque of all machines dyno’d.

Rob’s ‘Demo Monza’ bridges the gap between the highly strung Sprint motor and typical tuned motors but is early days yet in testing. Being a new engine it requires some miles under its belt before that can be established fully. All the dyno graphs and photos will be available on the Scootering and York SC web/Facebook pages, and if the event runs again, put it on your bucket list!