Malossi cylinder port

[wheels]

I’ve got a Malossi Sport 70 cylinder #3113570 to fit SYM (a/c horizontal)






Should the oval port on slip-in part of the cylinder match up with the port window on the piston skirt match up at bottom dead centre?
The cylinder I am using is a Malossi but the piston is not so I’m modifying it to work. Everything else checks out good I just have to cut the port window in the piston. 

[oldgeek]

The port in the piston is not needed in reed motors.
Make sure the pins that keep the rings from turning end up in the correct place, and not passing over a port in the cylinder.

[wheels]

Thanks for the reply. 
yes the ring stop pins are in the same spots as the Malossi piston except in reverse order which shouldn’t matter. So sounds like those ports act as a open/close valve for the air/fuel charge then. Good to know. 
the only difference in the pistons is the one I’m using is 2mm taller from the wrist pin centreline to top. (not top of dome) so I’m using a 2mm spacer under cyl to case. When piston is bottom dead centre lower part of crown is even with bottom of ports and at TDC even with cyl deck. I’ll check the squish as well. Sounds ok or am I missing something?

[oldgeek]

Sounds good, make sure the exhaust port is still covered by the piston skirt at TDC.