I do not think I would use over 2-3 lbs of air pressure to check for leaks...you could blow a seal. Use plenty of soapy water to find leak. It will show up as bubbles will form at leak. You are lucky if you did use 50 psi not to blow seals. Maybe instead of trying various carbs...you should try a easy to mount and adjust RCecell ignition. A different advance curve and with the ability to change timing more easy...you will end up with a very good engine. Capt,n