putting a new top end in my 2018 trail 500,looking at cylinders I see 2 options, Mark 1 or Mark 2, what are the differences or how are they identified ? also do the zforce 500 and 550 run the same engine, they are both listed as 495cc. thanks.

[2015 Z Force 800 53/Trail EPS]

putting a new top end in my 2018 trail 500,looking at cylinders I see 2 options, Mark 1 or Mark 2, what are the differences or how are they identified ? also do the zforce 500 and 550 run the same engine, they are both listed as 495cc. thanks.

The 500s and 550s are the same it's just in the US they are 500s and outside the US they are the 550. As for Mark 1&2, I see the two cylinder options but see no relationship between the head or any parts or piston or even the crankcase. This makes me think it was a mid-production modification to correct an issue.. but if so, why offer the faulted part. So...maybe the service manual would offer some clue. Probably not but it's worth a try

Thank you so much for the info,I did check the service manual and it just references tolerances for the cylinder.I figured it was the same engine,BUT I needed someone else to be on the same ship as I am. Thanks again.