I've got a 2001 Mountain Cycle San Andreas with what I believe is the stock Aftershock (not sure, as I bought it used and there are no stickers). I weigh 81kg (13 stone or 190 lbs). The shock is too soft and keeps bottoming out on not even very big jumps even with the spring wound all the way down. There are no marks on the spring to tell me what rating it is, but it is too soft. Can anyone tell me how I can work out what rating it is so I know what I need to get, and also what size do I need anyway? e.g. do I need a 650 X 2.8 or what? I have no idea.

Even if I beef up the spring will I then find out the oil's too thin?

Thanks for any help.