Ah, great stuff, thought so ! So it has to be 4 stroke right? Confusing since a two stroke bike... What is the reason for this? Cheers. The moving diagram is nice also, thx Edit: I have even more confusion now! I just looked at the Cagiva Planet Manual and it shows the Piston as having 2 Rings?? Both 91 version and 2001 version. Im confused as the piston i took out had only one ring? The two stroke oil is only for mixing with the petrol and it helps lubricate the piston. The rest of the engine, crank, gearbox etc... use four stroke oil. As for piston rings, well as long as you've ordered the right kit for your bike and year, then you'll be able to tell how many!