Yamaha RD350
The RD350 is the loop-scavenged two-stroke twin that defined affordable performance motorcycling in the 1970s, and it remains one of the most tuned engines ever built. At 64 mm bore by 54 mm stroke with a 6:1 compression ratio it is short-stroke and high-revving, and — unlike a four-stroke — its breathing is defined by port windows in the cylinder wall rather than by valves. That means port heights and widths are the tuning variables, and the exhaust pipe is part of the engine rather than an accessory. The calculator models the port-window areas against crank angle through the cycle, and the separate exhaust module sizes a matched expansion chamber.
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
- Port timing is set by the port height fields — raising the exhaust port raises peak power and narrows the powerband.
- Design the matching expansion chamber in the two-stroke exhaust calculator; the tuned length follows from exhaust-port timing and target rpm.
- Two-stroke compression is quoted here as the geometric ratio, not the trapped ratio measured from port closure.