outlet

Has anyone determined an ideal outlet size in their end cap with straight through mufflers? Too open and we don't run an ideal back pressure. I understand there are differences in engine size and work done but if there were a range responses a generalisation could be made for my...

I notice a picture of engine breather mods with one breather blanked off. I was told that in general more breathing helps freer revving. i.e every rotation of crank means 644cc of air must be displaced and then replaced from under the piston. In fact it was an easy mod for klx300's years ago. Is...