I have to add my two cents here. I just had my head milled 0.040" two days ago.

After cc'ing the chambers, I ended up with 20 cc's which was my target. My compression was 120 psi stock. It is now 148. 1200 ft elevation.

The stock head gasket measured 0.010". I have the old one in my garage if you want to measure it.

After talking to Allen Knowles from CT, he told me that, when running at Glamis - 300 ft elevation, anything smaller than a 20 cc chamber size with stock porting is going to make the machine slower.

I ran it briefly on 91 octane pump and so far it didn't detonate, but I'll find out for sure tomorrow.

T-5's, 320 mains and stock needles in #4 groove, foam pro flow w/ no airbox lid, boyesens.


As an update - rode the quad this last weekend and noticed a much wider powerband, a little more peak and no pinging on pump gas. It seems to come on the pipe sooner, rev out farther and have more punch overall. I would recommend this as the first and easiest thing to do after pipes...