Jerry beat me to it, but I can comment on the milling. I took off .039 (1mm) of a non stock head that had a smaller quench ring than the standard head and ended up at 10.3:1 static compression. If you do the standard head to .030 you should end up roughly around 9.8:1
Definitely invest in cleaning up the ports. Mostly cleaning up around the valve guides will make quite an improvement, especially on the exhaust side around the bowl and roof, and then smoothing all of the transitions to finish it off. Nothing fancy, but quite effective. The intake side needs very little in terms of material removal outside of opening up the port at the flange and smoothing that in, and obviously cleaning up around the guide again into the bowl.Pair it with a 30mm smooth bore carburetor and it takes the Hawk to quite a new level of performance. The PZ30 and VM26 clones are just too restrictive once you open up the breathing. Seeing as you have the EFI bike, it would depend on the size of the throttle body.
Is it worth doing? Absolutely. Will it give you the top end performance you are likely seeking. Yes, to a point. I have discovered the final limitation to top end performance to be the cam. Without changing the cam, what you end up with doing a ported/decked head with a larger carb like my PE30 or Jerry's PWK30 is a noticeable gain through he RPM range, but a big boost between around 4000-7000rpm. After that point the power starts to fall off due to the cam profile. What it does do is make the bike much stronger to pull taller gearing.
I am waiting on a new cam from Brazil as we speak to solve that last issue.
Like you, I don't tend to do stock very well lol.
Quote:
Originally Posted by alex_in_az
is it possible to remove the cylinder head with the engine still in the frame?
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Absolutely. I have a video where I did just that. No problem.