If I recall correctly my old Buick 215 cubic inch aluminium V8 gave about that pressure, but being the Powerpak option it had 11 to 1 compression and a 4 barrel carburetor. It seems very high for a chainsaw.
The main limiting factor to compression ratio is detonation. As the ratio increases, higher octane fuel is required. It may also be a factor in causing carbon accumulation - my old Buick engine had a very severe problem with that, because I put it in an MGB that only weighed 2000 lb, then drove it to work every day in the Melbourne traffic.
I think your saw probably either has a lot of carbon in its cylinder head, or more likely has been fitted with incorrect parts, such as a piston with a higher compression height (the distance from the center of the gudgeon pin to the top of the piston crown). In the good old days we used to do that to cars a lot. The ideal "improvement" to an old Triumph TR2, 3, or 3A was to fit Ferguson tractor cylinder sleeves (which increased its cubic capacity from 1.6 to 2.3 litres) and Chevrolet 6 pistons, which not only had the correct diameter to suit the Ferguson sleeves, but also increased the compression ratio to 10:1. This did wonders for the performance, but the heat rejection was a bit excessive for the original radiator. To be honest, there was an additional attraction to this modification: the Ferguson sleeves, being for farm equipment, were free of the 30% sales tax that applied to car parts. As an aside, the reason the Ferguson sleeves fitted the Triumph TR sports cars was that both tractors and sports cars used the 4 cylinder engine from the Standard-Triumph Vanguard car.
