Some quick easy gains are 50hp carbs, 50hp reed stop, or bending open the 40hp reed stops, fiber reeds, (not boyseens). Then if you want a little more take .015"-.025" off the head, just depends on your compression. Or 50hp head, heard there smaller cc's but never measured any of them before. I know the 60hp -70hp offered different cc heads through the years so the 40hp-50hp is probably the same case. On pump gas I wouldn't want to go much over 150psi. 160psi at the most Stainless 3 blade will help out some for holeshot and I normally see 1mph gain on top. That's just the tip of the ice berg. :mrgreen: But those are the easy mods that won't bother reliability and will produce noticeable gains. Exhaust tuner would be the next step but that gets a little more involved.