COMPRESSION TEST GAUGE READINGS.
Your Motorcycle will always have a higher reading on your compression tester gauge with a stock or low duration cam, due to the fact that you will be closing the intake valve earlier on the compression stroke. This longer effective compression stroke always delivers a higher gauge reading.
Installing a longer duration cam, your intake valve will close later, thus giving a lower gauge reading because of the shorter effective compression stroke. Some individuals feel that this is impossible, claiming that if it were true, why will your Motorcycle go faster with the bigger cam? The reason is that a bigger cam will have higher compression effect in the cylinder at higher engine speeds where all that additional valve timing can do you some good, but at lower speeds and especially at starter-cranking speeds, the effect will be lower.