Zero-Loss Gearbox Analysis
Montesa 4RT versus 315R
2001 Montesa 315R was 72.2 x 61.0 mm = 249.7cc
2005 Montesa 4RT (first year for 4RT) was 76.5 x 54.2 mm = 249.1 cc
From the chart, it certainly seems like the 315R has a big advantage at low engine speeds – and it does.
But that can be overcome with the proper overall gearing.
Regardless of the motorsport we are considering, it's always the driving force at the rear wheel that matters
My Zero-Loss Gearbox Analysis tool uses a simple spreadsheet that starts with a dyno table (digitized dyno chart) giving rpm and horsepower for as many points as is feasible. It's most straightforward to pick the same rpm points (in this case every 500) from each chart as this obviates the need for interpolation.
These values are then numerically manipulated so that torque is traded for engine speed, and vice versa, in the same percentage. This maintains the horsepower but artificially forces the rpm range to be identical for both engines.