It’s nice to see someone do this test that knows what they’re doing. Almost all the other videos on KZfaq on how to do this test are wrong. Most of them tell you to pressurize the tester before you plug it into the cylinder adapter hose. Which is dumb as hell. Lol.

HI i have a CubCadet mod 12a 18mz596 self-propelled pushmower with a Powermore series 700 engine that has recently been pushing oil from the breather /air filter onto the deck and gotten progressively worse i ran the breather tube into a plastic bottle on the deck and it fills up about 250 ml in about 10mn of running engine ..the crankcase is pressurized forcing oil into the bottle .i removed the flywheel and disassembled the pcv ,removed fiber disc ,tensioned spring and cleaned the metal filter screen and cleaned the drain hole and reassembled it .then i removed the cylinder head and cleaned the head, valves ,spark plug ,piston head face and reassembled .no scoring of the cylinder wall . I've had the mower since new and always maintained, oil changes etc . after changing the oil and adding .6 ltr of 10w30 Castrol GTX, i ran it and then checked the spark plug expecting to find it fouled but it was completely dry and clean . i thought it might have been a cylinder head gasket but its intact and sealed ,then i thought it might be piston rings but it doesnt burn any oil or smoke . would the oil ring be plugged/defective turning it into an oil pump? If you didn't see the oil container and notice the crankcase pressurization you would think it was a new mower as it starts right up and runs fine other than pumping oil out of the filter .Appreciate any insight you have .Thank you Dave

Also removing the oil fill plug let's you hear air flow (if past rings).

Good video

Hey thanks for the quick response , When i purchased it new, it was the first lawnmower i have had that recommended 10w30[sticker on shroud ] i had always used sae30 so i called MTD and a couple of Cub dealers and the response was that it was a Modern Engine Design so use 10w30 . When i contacted MTD recently the service rep now said it should be SAE30 as well , apparently they have experienced failures with 10w30 [mine is a city size lot 55x110 no severe use but makes me wonder if i had used SAE30 would i have has any issues now] Also said the crankcase pressure should be no more than 6lbs,, and he's not sure why its so high to push oil out the filter. MTD now have a ring set for it [ I called MTD and it is in stock] which according to the area dealers it is unavailable and you must buy a short block for $250 for a 10 yr old lawnmower? So i think i might change the oil again with SAE30 and order a ring set and new head gasket and try the head gasket first in case there is an area on the gasket that isn't properly sealing and allowing pressure to build in crankcase although prior witness marks showed nothing I did a compression test and the results were lower range 50lbs [not sure how accurate gauge is] so i guess the only option is to disassemble it and check the rings and cylinder bore for wear /out of round ,scoring on lower surface of cylinder walls OR run it as is with pvc vent pipe inserted into a bottle ,then pour contents of the bottle back into the engine once i finished cutting the front lawn ,and again when i finish cutting the backyard until it completely quits running . But i am puzzled as you said it should be burning oil /smoking or fouling plugs and coming out of the exhaust in some form .Always starts right up and sounds as it did new .the grass never gets long enough to challenge or strain the engine

ok so my engine is supposed to be 1/4" past TDC for this test. Did you do anything to prevent your crank from turning when you applied air to the cylinder? Imy engine is on a Husky tiller and when I apply air the engine flywheel turns changing piston position.

You have to remove the exhaust rod to check compression

Would that issue cause the engine to blow white smoke ?

can some of that compression be coming through the cam tappets.

Liked. I don't have acess to the leak down tool or compressed air. So I can't do this test. But I have a question for you or anyone willing to share info. Since the OHV Engines. Briggs & Stratton Intek in my case. Have a compression release valve for easier starting. What's the minimum amont of compression I can have and the engine still start fairly easy? Thanks in advance.