Firstly I'd like to say Hello, I'm new to the forum and this is my first post. I live in the North of England here in the UK and have found this site to be more relative to my bike so decided to join up.
I'm rebuilding the top end of my YZ450f which I have just bought. The bike came with no history of maintenance and the previous owner quite openly admitted he had no idea if anything had been done piston or vavle wise. He had changed the oil during his 6 month ownership and kept the air filter squeaky clean but apart from that, the bike ran so he rode it. I checked the valve clearances which showed them all in spec except the middle inlet which is 0.5mm so I thought I would strip the engine down to the bottom end to see what condition it is in, and to be fair, it all looks pretty good. I will be replacing the piston and rings along with the valves springs, seals and timing chain as I read these are relatively cheap parts and have been known to fail causing expensive damage. I will be changing the valves too if they look worn once If got them popped out.
My question is, the conrod bearing onto the crank has quite a bit of movement in a rocking side to side way. I can feel nothing vertically and very little horizontally (well within tolerance), but if I rock the conrod at the little end, side to side in a pendulum type way, I have about 1.5-2mm movement at the little end. Is this acceptable and ok to leave?
Also, which piston do you guys recommend or should I just stick with the OEM parts?
Thanks in advance.