Chainsaw Repair

The spec is not for the engine hold the full vacuum forever!

 There are many variations on how to go about pressure testing a chainsaw crankcase.

If you have a repair manual for your chainsaw, there is likely a crankcase pressure testing tutorial in the repair manual. If you have several different manuals, you may find several different ways to perform the pressure test?

The basic factors are:

The chainsaw must have the cylinder sealed to the crankcase.

The muffler and carburetor must be sealed off. This can be done with solid gaskets, inner tube, plastic or metal pieces, or combinations of these.

The pressure used is 1/2 atmosphere which is .5 KPa or 7 lbs pressure or 14" of vacuum.

Pressure is easiest to do as any leaks can be found with dish washing soap bubbles.

Crankshaft lip seals should also be checked with a vacuum due to their design. A chainsaw can check OK under pressure but absolutely fail the vacuum test due to the crankshaft seals.

The pass/fail parameter is that the crankcase should not loose more than 1/3 of the test pressure within 30 seconds.

There are a lot of ways to create the pressure or vacuum.

The most accepted way is to use the automotive tester for bleeding brakes and checking vacuum switches.

The Mity-Vac 8500 is the definitive tool (Ebay?)