Honda NSR250R
The NSR250R is Honda's 250 cc two-stroke V-twin, the most technically developed of the Japanese quarter-litre sports two-strokes and a bike whose engine was built to grand-prix practice. At 54 mm bore by 54.5 mm stroke it is essentially square, running 7.4:1 geometric compression — high for a two-stroke and part of why it made its power with unusual efficiency. The preset models one cylinder. For anyone rebuilding or tuning one of these, the value of simulating first is that port work is irreversible: metal removed from a cylinder cannot be put back, and the model costs nothing to run.
Preset parameters
Values below are the preset the calculator loads — you can change every one of them in the form. Angles are absolute crank angle (CA) on a 0–720° cycle.
Reference figures
Manufacturer figures carried by the preset for comparison. They are reference values, not calculator output.
Notes for modelling
- Model the port change before you cut: raising the exhaust port by a millimetre is a permanent decision.
- Per-cylinder results; multiply by two for the V-twin.
- The expansion chamber must be re-tuned after any change to exhaust-port timing — use the exhaust calculator.