Compression test pressure is way too high, unless it is running very mild cams with very high compression ratio pistons.
How can you tell what size of engine you have? - you could do a "pump" test (measures cylinder volume on one cylinder)....for the home mechanic, this is quite easy to do, but cleaning up afterward takes a bit of time and effort.
1. Remove #1 spark plug and bring piston 1 up to exactly TDC on the compression / power stroke (valves closed). Set up a good steady light source directing light into the spark plug hole so you can see the piston top.
2. Carefully fill the cylinder up to the bottom (not top!) of the spark plug hole with a light weight oil like kerosene or diesel fuel (best) or solvent (second best). This only takes about 2 tablespoons of oil. Don't spill any oil over the top of the head.
3. Precisely fill an accurate graduated measuring cup or similar measuring vessel (I robbed the science lab at school of a 500mL beaker) with oil or solvent to at least the 300 mL mark.
4. Rotate the crank precisely 180 deg. (use the TDC mark for cylinders 2 &3) so the piston is now at BDC and very carefully fill the cylinder just up to the same level as it was in step 2, without spilling any. Look at how much liquid is left in the measuring container and subtract that from the amount it started with, and you have the displacement of 1 cylinder ( 1 mL = 1 cc ).
5. Multiply by 4 and you know what displacement you have.
6. Now clean up and get rid of the oil - you might try sucking it out with a wet / dry shop vac. as you slowly turn the crankshaft bringing no. 1 piston back up to TDC, or you could extract it with a small diameter length of vacuum hose and try to syphon it out.
Avoid just using the piston to pump it out using rags to wipe up the mess, or you will get a lot of oil in the ports and the engine will smoke like crazy when started...
Don't put the spark plug back in until you are absolutely sure the oil is out, or you could hydraulic lock the engine and do some pretty serious damage....
2-04 R1, 81 CSR1000, 81 LTD1000, 2-83 GPz1100, 3-79CBX, 81 CBX, 3-XS650, 84 Venture, +parts
Quote "speed costs money...how fast do you want to go?" (Which Z movie?)
Universal formula for how many motorcycles one should own = n + 1, where n is how many motorcycles you own right now....