Any way to determine compression ratio?

There is a way, but unless you have the engine mounted on a stand, it isn't practical and the measuring tool kit is expensive.

It envolves rotating the engine on the stand so that the sparkplug hole for the cylinder under test is the highest spot on the engine. You will pour light oil in the cylinder and you don't want there to be any air pockets to upset your meaurements. Start by setting the cylinder under test at TDC. Pour in light oil using a gradualted glass cylinder maked off in CCs. When the oil becomes level with the spark plug hole stop pouring the oil and note the quanity in CCs. Crank the engine to BDC and add more oil, carefully keeping track of the number of CCs you pour in. When the oil becomes level with the spark plug hole stop pouring the oil and note the quanity in CCs. Divide the BDC oil figure by the TDC oil figure and the resulting number is the compression ratio.

See Search Results for burette - SummitRacing.com for the kit with the measuring burdette for measure the oil.