Motorcycle Repair: Leak test, stroke engine, leak down test

Question
Hi, what is the main reason for a leak down test on a two stroke engine? Also how do you calculate the mix, oil to gas if the mix calls for 50:1 for an imperial gal of gas? thanks.

Answer
The pressure/leak test on a 2 stroke is to test that the crankcase seals are all okay. Any leaks at the crankseals will either draw in air or transmission fluid ( both changing the fuel air ratio).

The ratio is a ratio, no matter what the measure is. You will need to determine the cc or oz of the gallon of fuel and divide in the cc or oz of the oil to determine the correct 50:1 mixture. It is just 50 parts fuel to 1 part oil (I assume synthetic at this ratio).

Bill Silver