These are rubber expantion plugs that you use to plug the exhaust and intake. These can be hard to find but if you have a pep boys near by they have them, or a plumbing house should have them also. The second picture is of my compression tester with the gauge removed and a schrader valve screwed in it's place. For this to work you have to take the schrader valve out of the end of the compression testers whip that screws in to the spark plug hole or you can't put air in the engine. Use a small foot pump for a bicycle or something similar to put six psi in the engine, do not over pressure the engine. If the plugs come out things can get busted that includes your face make sure the exhaust and intake are clean and dry of oil and put the carb clamp on the rubber boot and tighten it just like the carb was in place then tighten the plug. The engine should hold six psi for sixty minutes. If it does not then use soapy water in a spray bottle to look for leaks. To check main seal put soapy water on the crank case breather tube if it blows bubbles the right side crank seal is leaking. To check the left seal you have to remove the mag and spray soapy water on the seal. If the left seal is leaking it may be obvious, do to, gas and oil behind the mag.
