[rpduc]

So how much rattle is too much?
This is my first modern 2 stroke - at low to mid revs mine sounds like a chain slipping over a cog (not loud though)
Is this the norm please?

Very difficult to quantify over the internet. I was in the same position last summer, new to modern two strokes and used bike with a rattle that just did not sound "right" to me. I rode it for the summer hoping it was one of the "normal" rattles people here described but it seemed to get progressively worse. This winter I had it out on the ice few times and decided something was not right. Seems to have been piston slap in my case but I'd think that unlikely on a '08 300 unless it's been ridden a lot.

In my case the rattle was more consistent when pulling down low than the rattles others described as more intermittent or occasional and attributed to chain slap, PV etc.

Sorry haven't delved into the PV govenor.