I got my 4.2 back from Brison. I haven't had time to try it yet but the tag says it does 7490 rpm with a 22x10 zinger pro. My understanding is this is with an open exchaust. I have a 22x10 zinger pro so I'll have to see how it runs here. But in the Laser I run a slimline pitts exhaust that is restrictive. I'll have to do some testing to see how restrictive. I'm impressed with the way the motor came back, they now cover the cylinder and carb with some heat shrink plastic. I'll post when I have it running.

Jerry