Calling all porting pros, check these pics!

[K-nut]

Here's my story: '86 engine just rebuilt the motor from the crank up and compression is only 125 psi (know protocol and used two different testers). Also passes all leak tests, new top (and bottom) and bore (1.5 over). Pulled cylinder after only 1.5hrs of ride time and cylinder wall/piston all look good - no scoring, blow by, etc. And while the bike is hard to start (know protocol) it otherwise seems to run strong, unboggable, no detonation, etc.

I continued to pull the jug and it looks to be very tinkered with, so my question is: Could the relieving of the exhaust port/bridge to such a degree (or any of the other porting) lead to the compression being so low, ie 25%+ from the norm? And as the work looks unevenly done (on all bridges), by perhaps another amateur mancave mechanic, does that even matter?

Is it recommendable to reduce the squish clearance and mill the top of the jug and head, perhaps up to .5mm total (ie .25mm each)?

Appreciate any feedback from the porting pros, upon looking at the photos. Thanks in advance!

[Roostius_Maximus]

the intake side is stock, the chamfer of the ports is done with a fairly large tool, not pretty but it ain't hurting it. the bridge looks crappy, cant see why it'd be trouble.
what does the ring pack look like? what is the ring end gap when in the bore at 1/2" from the top, just above the transfer ports and just below.
It'd give us some idea of the cylinder taper or what might have gone on.
piston pics?

[K-nut]

thanks for the prompt reply. will get a measure on that and revert.

here's a piston shot. a few slight vertical scratches and just below the second ring you see where the grey is worn off which matches with some glazing in the cylinder wall just above the exhaust bridge (other pic). otherwise the inside of the jug and the hone all looks fine.

[crashtestdummy]

My experience is telling me that there may be some sharp edges left over from hogging out the exhaust ports. What could be happening is the sharp edges get glowing hot and then chip away a little at a time and get in the cylinder. I think there are too many scratches and abnormal wear for an engine with 1.5 hours on the clock. I was a CNC cell machinist at Federal Mogul for 3 years making pistons and sleeves. Sharp edges were frowned upon by quality control just for that reason. I would use a buffer and polish up the ports to remove burrs and sharp edges.

[Roostius_Maximus]

...I was a CNC cell machinist at Federal Mogul for 3 years making pistons and sleeves....

sweet