I have a few o series saws I want to pressure and vacuum test. Curious as to proper procedures for this. Have an 026, an 028, and an 038 magnum. I planned on blocking of the exhaust and the carburetor on the airfilter side then hooking my vacuum and pressure tool the the impulse nipple on the crankcase. My question is do I have to plug the disconnected impulse hose? Is it possible for air or vacuum to leak through the carburetor where the impulse line connects to it?