Honda CR500
The CR500 is Honda's 500 cc motocross single, and it is the largest-bore two-stroke in the preset library at 89 mm. A single cylinder of that size firing every revolution produces the torque the bike is notorious for, and the 8:1 geometric compression is high for a two-stroke of its era. Big-bore two-strokes have a specific modelling challenge: port width is limited by the ring, so extra flow area has to come from height, which pushes timing and narrows the powerband. Running the preset shows where that engine sits on that trade, and what moving it costs.
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
- A single large cylinder means the inertial forces are unbalanced — check the dynamic results, not just the power figure.
- Port height is the main flow variable available on a bore this size; the width is mechanically constrained.
- The tuned pipe follows exhaust timing and target rpm — size it in the exhaust calculator.