I've got a few "modified" engine versions at home, You CAN tell the differnece from 160 psi to 205 on a pull rope take my word for it, you can literally separate ligaments if you fail to flip the decomp. lever. Now do you see a change in performance, not really 25 bucks worth of sprockets would have been a cheaper way to go, but not as fun.

And the duration of the cam changes the volume of the compression theoretically because: high intake low exaust duration means you are "preloading" the cyl with excess fuel air product using the suction of the stroke to fill the cyl ;compression is forced to increase because of the volume you are compressing with the avail. space, is reduced by molecular mass; realistically doing the same job as a dome piston with less chance of metal parts touching which should never touch. Now, if you go 3 bores over (about 230cc) with a high duration cam polish the exaust port, widen the intake by 2 to 3 % you can take your little 200 into a 60% increase in HP, but little or no increase in torque, which for me is more viable in an atc than massive HP

IMHO,Darrel