My bike w/ pics & major question about stroke length

[Joshua_NZ]

Yo so here is some pics of my project.

I’m just doing some more dermal work on the cylinder & piston & I have gotten to a point where I am confused & don’t want to go further without clarification.

So I’ve been running this engine for just a few weeks & I’ve taken the top end off to do some more dremal work.
As you can see in the first pic here I can see a highly polished area in the cylinder’s coating. This is clearly from the piston rings rubbing ever so slightly.
What confuses me is if I look at the ports with the cylinder at these positions I find a huge restriction being caused by the piston skirt.
Can you see this too or am I mistaking the stroke length with just where the rings are polishing not the top of the piston.
Making no sense ... lol, just look at the pics:

Cheers guys.

 

[6blueoval9]

On the intake port only...move the piston to top dead center and mark a scribe on the piston where the skirt blocks the intake port ,then grind or cut the skirt where scribed to unblock the port.

Widen the intake port at the cylinder 1mm per side..leave the bottom and the top of the port alone.

Do the same to the exhaust port but cut the top of the port also 1mm...leave the bottom alone.

Get a good pipe and carb and enjoy.

Pic aren't showing by the way.

 

[crassius]

note that trimming the skirt at intake will cause intake to close later, so be prepared for a bit of extra spit-back thru carb and a bit less gas mileage