Leakdown test

[bwestbrook]

If working on a 2 cycle you block off the exhaust behind the muffler, block off the intake behind the carb. Use a mityvac to check pressure and vacuum of crankcase, never exceed 7 pounds of pressure or vacuum. Crankcase if sealed should hold pressure and vacuum.

You can have leaks around the sparkplug, intake manifold, crankcase gasket, crankshaft seals. If 2 cycle won't hold vacuum then pressurize crankcase and submerge crankcase in some liquid like parts solvent and look for bubbles.

4 cycle there is a special gauge to determine how much is leaking in percent of loss compared to input pressure.

ILENGINE.... Exactly you explained it much better than I was. Thanks. It is a 2 cycle I am working on.

 

[reynoldston]

Thanks now when I see leak down test I will know what they are talking about. This would of been a good test back in my old snowmobile days when I worked on two cycle engines. I now understand what you are talking about. Like I said earlier I know that the crankcase is pressurized for a two cycle engine to run right. Really not much of a 4 cycle engine test and something I never did. It sounds like you would have to make something to block off the intake and exhaust manifolds and any vacuum ports. Also you would need a vacuum pump with a gauge. Just never ran across anything like that but will keep my eyes for it now. This is the second time I have seen it on this forum and the first time I never found out what they were talking about. Another thing I have always heard it called cycle not stroke, I guess just where I live and my way of saying it.

 

[bwestbrook]

You can just take a piece of rubber like a tube for a tire a mount the carb and exhaust back on to block it off.