JCStokes, yes, I machined .130" off the top of the cylinder.  I was on the fence for awhile trying to decide whether or not to remove the material from the top or the bottom.  

Taking it off the bottom is a bit harder because you have to stop the cut right at the cylinder liner.  It also is a bit more critical to maintain perpendicularity so you don't end up tipping the cylinder to the right or left.  Taking it off the top is easier to machine but there's that pesky oil feed groove to worry about.  In the end, the design made it easier to decide.  Seems there is a flange in the bottom of the liner that locks the liner in-place.  I had no idea how thick the flange is and didn't want to risk lobbing it off, so I took the material off the top.

Here is a shot of the flange in question.

Here is a shot that shows the new cylinder deck after machining.  You can see there is no longer a raised flange, its now flush with the top cooling fin.

Jesus, 130thou is over 1/8 inch, will this affect flow/ quantity in the oil groove, and what does the oil grove feed?

What is total advance now? Seems a really happy motor runs about 28 degrees total advance. Can't think of any that did less. Lots of crappy combustion chambers ran a lot more.
Most welcome for the loan of the jigsaw head.
I honestly didn't think it would be .130" cut. Judging by the numbers being thrown around, I knew the bike had zippola squish.
As far as I got was to think about extending the tensioner, and putting a piece of steel rod in the center of the spring to limit the amount of travel back into the tensioner. Was going to put a window in the side of the cylinder so I could check tension cold and hot and come up with an ideal cold chain tension.
Got seriously sidetracked on my project.
Just this past week I finally got back to it.
Did the double-wide sprocket bearing and the modified axle spacer. Removed a bit of the exhaust donut.
Then I spent a ton of time on the side stand (modified 675 Triumph). Then the muffler bracket. And........

  Mike ,If the problem is to high of a compression ratio , rather than retarding ignition timing , or machining the piston dome , due to your static compression being 245 psi , I would  backup a bit and remove the advance in cam timing.  the exhaust valve's early opening may have something to due with the strange  noise your hearing , higher chamber pressure still has to find it's way out of the head through the same size valve seat. the intake valve's earlier closing has also boosted your CR ,something I didn't see taken into account in the compression formula you used that arrived at 215psi . You could also drop CR AND increase the effectiveness of the quench you've created by the use of Singh grooves. the loss of compression might be made up by the increase of combustion efficiency .
          As far as I know ignition timing advance stops a about 5000rpm, the fact that your getting 7000 rpm out of second gear (500 rpm over redline) hints the  ignition is pretty forgiving ( and fast with the sparkplug centered in the head) .I really don't see that retarding it farther would be necessary, or that you would see a perceptive change. A 2-4 degree change might be negated simply by changes in elevation.(but may show slight improvement as you get closer to sea level).

Lancer, I took a look at the scenario you described.  Milling .025" didn't tighten up the quench but did reduce combustion chamber volume.  Taking .015" off the cylinder tightened the pseudo quench a bit (reduced it to .175"), but IMO not enough to improve combustion any appreciable amount.

I had to make an assumption regarding your finished combustion chamber volume.  I assumed that milling .025" off the head surface would be approximately equivalent to 70% of a reduction in volume due to reducing cylinder height by .025".  So I figured out the volume of a 3.700" cylinder .025" tall and took 70% of that.  It worked out to 3cc.

I reduced combustion chamber volume from 57cc to 54cc and plugged all the numbers into the rbracing calculator.  The result was a static compression ratio of 8.73:1.

Then I used that value, along with an intake closing point of 40 degrees ABDC @ .050" lift (data from Dave's Stage I), and an elevation of 652 feet (based on your location) and plugged that data into the dynamic calculator.  That predicted a cranking pressure of 157 psi.

Like I mentioned earlier, I'm comfy with the static calculator, but the dynamic I'm not so sure for our application.  It's a Harley specific calculator so there might be induced errors when applied to a metric cruiser.

What sort of performance gain did you experience with that setup?

BTW, how did you puncture your crankcase?

This shot shows the Wiseco and the stock piston sharing the same wrist pin.  If you look close, you can see the flat top portion of the Wiseco just slightly higher than the stocker.

Batman, I originally planned on using the cam retard trick if this thing posed a compression issue.  I've used it in the past and it can provide some relief under the right set of circumstances.  I figured if there was too much compression I would experience the classic symptoms, hard starting and knocking when I lugged the engine.  Closing the intake later starts the effective stroke later. That makes the engine easier to crank and tends to eliminate detonation when lugging the engine at low speed.

That's not the case with this engine.  I'm not even sure if it actually is detonating.  I simply don't have any experience with cranking pressure this high running on pump gas.  It starts right up and I don't get any audible indication of knocking doing day-to-day street cruising.  There's no visible indicators either, like ugly spark plugs or sand-blasted piston tops.  All seems normal.  

The only time I think I might be hearing any bad noise is at high rpm.  Under that condition, the retarded cam timing will enhance inertia filling and bring the pressure up rather than bleeding it off.  For now, I'm going to leave cam timing set right on the factory marks.

I'm not sure about Singh grooves.  I really don't get the concept.  I viewed one of his infomercials on throttle bodies but it just didn't seem logical.  Maybe I missed something.  You've mentioned that you incorporated those grooves into your engine/carburetor.  Do you have any pictures you can share so we can get a better idea about what they look like, where they go, how to cut them, angles, depths, etc.    

My primary reason for pulling out timing is performance.  I think it will make more power with less ignition advance.  If that provides a little more margin for preventing detonation, bonus.  It also gives me the opportunity to play with that ignition pickup and figure out a good way to move it around.  It would be great if the system had a vacuum retard like a Harley.