compressed air?

Temperature of what? The cylinder head...yes, with an infra-red 'laser' thermometer.

VICTA two stroke engines are air cooled. They are cooled by ambient air and by the rotation of the engine flywheel which has fins all around it. The engine temperature is fine.

Theres no way in the world it would run with a 5mm gap lol. That's freaking huge. Even 0.5 mm is way out of factory tolerance

@Mowtoe Gee Believe me, it ran. Just had no power lol.

We have tested compression with the decompressor on and with it replaced with a spark plug. We found that with a correctly functioning decompressor the reading is the same. If your decompressor may be faulty replacing it with a spark plug would be a good idea.

PushMowerRepair.com Thank you

Shesti76 Can you do a video on piston & cylinder head visual inspection (by removing the exhaust) and commenting when it needs to be replaced / honed, because sometimes compression can be good, but piston (cylinder) can have scratches due to overheating or bad mix. Cheers

The decompressor will give a lower reading LoL. Its purpose is to allow less compression so that it is easier to pull start. Educate yourself before acting like you know what you're talking about. After it has started running it allows a higher compression. If you are getting the same reading with the decompressor bypassed then the decompressor does not work properly. This means you will have a lower reading with a PROPERLY functioning decompressor.

I have the same mower & the reading is different with the decompressor removed & plugged up with a spark plug. I got a reading of 95 PSI with the decompressor in place & 107 PSI with it removed & plugged up with a spark plug. So I knew I could chase up other faults on the Victa engine, it still needs new crankshaft bearings as water has got into the engine but I need to rekit the carby & make sure everything is good before stripping the engine down. I test the 4 strokes similarly by removing the exhaust rocker arm to bypass the decompression mechanism in the camshaft. It would be a good idea with the Victa to squirt a bit of oil in to eliminate the chance that it's not a blown cylinder head gasket,that hopefully the worst it could be is a broken piston ring & not a damaged cylinder & piston. If the engine needs a new piston,then it needs a rebore & oversized piston fitted. I have a Briggs & Stratton engine which is getting worse as far as run quality goes,it was 97 PSI & now it's at 90 & is getting very hard to start.

Yes...got to UAP and get a large can of compression

I think what you should say is they are not 100% accurate.

Two reasons that could cause this: 1. Cheap compression testers have the Shrader valve (the valve that reads compression) at the end of the line instead of right at the spark plug hole, which reads inaccurately low because the piston fills up the tube in addition to the cylinder head. 2. Newer Briggs & Stratton engines have compression release mechanisms on the camshaft that make the engine easier to start. They disengage after the engine revs up a bit but give low compression readings when you're just pulling the rope. Spin the engine with a drill (should be 15/16 socket, you'll need a corded non-impact/non-hammer drill) and you'll get a better reading.