Cylinders / Pistons


The 250, 280, and 300 engines all used a common 60mm stroke and the same crankshaft.  Bore sizes and actual displacement are as follows:

250 (72.5mm bore) 247.7cc

280 (76mm bore) 272.2cc

300 (79mm bore) 294.1cc

Each piston will be available in multiple sizes to make the piston-to-cylinder clearance perfect.

Size A: 72.46mm and 75.96mm and 78.96mm

Size B: 72.47mm and 75.97mm and 78.97mm

Size C: 72.48mm and 75.98mm and 78.98mm

GasGas, Vertex, and S3 all are possible sources for replacement pistons and rings. 

TR280i transfer ports

TR280i exhaust port

280 Crude Port Tracing

TR280i exhaust port outlet

TR280i stainless exhaust spigot

Port Timing

These measurements were made with a degree wheel.  They were taken when I first got my TR280i.  I would not bet my life on them, but they should be close.

Exhaust duration: 158 degrees

Transfer duration: 135 degrees

Blowdown duration: 23 degrees

I then back-calculated that the connecting rod needs to be 130mm (center to center) to get dial gauge measurements to agree with the degree wheel.  

Note: the connecting rod center to center length has been measured at approximately 118mm.