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Author Topic: Need Ideas For Home Made Pressure Tester,  (Read 6903 times)

Offline MotorGeek - Jerry Hall

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Re: Need Ideas For Home Made Pressure Tester,
« Reply #25 on: November 09, 2017, 12:25:13 pm »
What happens if you put in more than 10 p.s.i. Into the crankcase?

It could possibly push the crank seals out of the cases if the seal was not installed correctly or the crank seal bore is loose or damaged.  The crank case can experience around 20 PSIG in a healthy highly developed two stroke. 

A pressure check will show a leaking gasket or crack in the cases or cylinder.  A pressure check will NOT always show a leaking crank seal.  For a crank seal that has worn pressure lips, more pressure will make the seal lips grip the crank "tighter" and leak less.

There are two lips in a crank seal.  One lip is made to hold pressure and the other lip is made to hold vacuum.  If the pressure lip leaks, it just causes a slight loss in power.  If the vacuum lip leaks it causes a lean condition and or it will suck oil from the transmission. 

Pressure checking a two stroke engine will not usually tell you if the vacuum lip is holding or leaking.  It is not usually necessary to pressure check an engine that has a leaking vacuum lip.  The engine will exhibit lean symptoms by having the ring-ding-dings on deceleration, high RPM idle and or acts like it is running out of fuel. If the pilot jet is not restricted and the correct size, the engine probably has some type of air leak.

Engines that have experienced a broken piston skirt, often have damaged cases and will leak air.  Engines that have had welding done on the cases will often leak air.  Engines that have had a big end bearing failure will often have case damage and leak air.

Pressure checking an engine is a diagnostic tool that we seldom have to use.  It will not hurt the engine but can be time consuming especially on the engines that have power valve systems. 

 

 

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