[beatr911]

The rage at the Honda marketing department seems to be friction reduction. This is likely a contributor to the reduced fuel useage seen of late. If you are increasing compression with an aftermarket piston, ask about a low friction coating. If you are milling the head, consider that it will retard cam timing making the engine run a little stronger at higher RPM, at the expense of lower RPM power.

I understand that friction reduction coatings can be used on other parts of the engine as well. Make experience with friction reducers a consideration when choosing engine builder.

The compression ratio chosen depends on the grade of fuel you plan to use. The 200cc Chinese derivative of this same motor that I had probably wouldn't like higher than 9.0:1 on our regular gasoline. I'm guessing your fuel is a higher grade. Consult the TTR 230 forums as this engine family is widespread and long lived in Yamahas production runs. Again your engine builder should be able to answer this question.

As for polishing, it can help with pre-detonation if there are some burrs or protrusions in the combustion chamber, as you know. Also, I've had success in smoothing any sharp transitions in the intake, like around valve seats.

A co-worker of mine has been doing the motoman.com high velocity intake service for racing quads for several years now with success. He says that the dyno has shown a good bump in bottom end and mid-range with no loss, or minimal loss of top end. I didn't get it done on my 200 before selling but do know that they have very large ports that could very well benefit from it. No idea how it affects fuel mileage though.