Pressure Testing your 2 Stroke Chainsaw Engine Whatever brand you have.

Many times we get weird or odd problems associated with hard starting of chain saws well below is a guide to finding a rather serious problem with two stroke engines.

I f we have either a leaking seal from old age or a lip of the seal lifted from a foreign object or a leaking gasket then we have no pulsing in the crankcase so during the cycling of the engine which has the crankcase in both positive and negative pressure if there's an airleak then there will be no way we can get the fuel pump to draw fuel to the carby and or the engines pumping ability will be less in recharging the cylinder.

Now i have taken the liberty of pinching a few pic's i have found off the net.

1. We need either a pressure pump or a vacuum pump to carry out this test.

2. Cut some rubber stips big enough to cover the intake manifold to cylinder port and after punching two holes in it fit the rubber strip between these two parts and nip them up.

3. Now do the same to the exhaust port.

4. Personally i use a proper pressure testing pump as i'm an ex-dealer in Mac saws but you could make or use a small length of rubber tube from the pressure pump to the pulse fitting on your saw but not all saws have a pulse fitting.

5. What i did and it require's a little messing around is use an old spark plug and remove the centre of it and braze in a piece of tubing to accept the rubber pulse line and Bob's your uncle.


6. Once the saw has been fitted out with the sealing blocks or rubber strips it's time to pressurise the saw now don't exceed more that 5 psi otherwise you will blow the seals.

Once the saw is at 5psi it should hold that pressure for at least 5 minutes but a very very slow bleed down is OK.
If the pressure drops away quickly you can now work out which seal or gasket is leaking by running a bit of soapy water over the seals and or gaskets and watch for the tell tail bubbles
You can use either a Vacuum or pressure Tester
Check with you local hardware store as you may find a fitting like these brass fittings that screw straight into the spark plug hole
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