Goathier

Thanks for your response, appreciated a lot, yes it already has a B piston and from the video I listen to I think I was just not use to the 2 stroke sound + maybe a little slap. That's an awesome tips, I guess this will still seal even thos there is a little grease ?

I open it up just to be sure and everything seems to be in specs. There is absolutly zero movement up and down on the crank and same for the piston. Thanks!

Didn't knew them, thanks a lot !!

Thanks ! I will look into that but still not sure if I can get Beta parts, made a few calls but not a lot of dealer. If I open it, do I need new gaskets or I can reuse the same if they look fine ?

Hello! I read a lot about the problem and still confused if it is considered 'normal' or in very bad shape. The rattle is every stroke, but when I listen to video of any trials bike I can hear that same sound. (I never had a trial near been close to one, it's very niche sort of bike over here) The engine has 160 psi of compression and start first crank every time. Engine sound I recorded, I think it sound just a bit worse in video than on real life. Thanks!