Does anyone know?

[wvtri-z]

I have a tri-z that I just split the cases, the crank is different and the connecting rod is longer than stock. The piston is different also. The cylinder is the same as stock all but the extra port cut into it and ported. It also has the 5mm cylinder plate. Anyone know what i have? The bike is awsomely fast and arm jerking. I bout it in 97 from a guy that iced race it. Thats all the info i have.

[wvtri-z]

In the late 1980s Ohlins of Sweden made a limited number of top end kits for YZ250s that converted them to 360cc, to make them FIM legal for the GP 500 class. I don't know of any source for spare parts. You'll have to convert it back to a 250cc when it wears out. You can use YZ250 top end parts. Perhaps a breaker like MXB in Wales can help you. Regarding the crankshaft, the Ohlins kit uses an YZ490 connecting rod, which is 10mm longer than an YZ250. You could use a spacer plate from Yamaha, available as a separate part in the long rod kit package. The plate is used with two base gaskets and compensates for the longer YZ490 connecting rod.