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G'Day all,
I'm going though the process of repairing a Honda push mower that went from running fine to not starting with little no warning.
There's a lot I've looked at to get to this point (new carb (had a spare)), checked ohms of coil (under 9k), new plug (twice), new fuel (with tank drain - twice). I couldn't get the flywheel off (don't have a puller) and soaking the stem in wd40 overnight before trying to tap it free with a wooden mallet proved fruitless. I was able to confirm that the magnets lined up perfectly with the coil pickups at TDC so am satisfied the timing is correct. Then checked compression. I didn't start with compression because it wasn't smoking, started perfectly previously and gave no warning - literally one start to the next a month later - running to not starting, AND I had to borrow a compression tester . Once I checked compression I thought I was using it wrong - it was zero. Then remembered the decompression valve, so removed rocker cover and took out both pushrods. Compression test then went to 30 to 35 psi. Okay better, but still a problem. Teaspoon of wd40 in the combustion chamber and it came up to 40-45ish after a few pulls. I was about to right it off as rings when I heard something as I turned the flywheel by hand: When near TDC with the rocker cover off and the push rods out, I could hear air hissing past the valves. I was going to check the head gasket anyway, so I spent the extra 5 minutes and took off the head. Gasket/head was good with no sign of damage. Chamber was okay, minimal carbon. I popped of the retainers and valve springs and checked the seats. Honestly, very minimal wear - almost no pitting and even surfaces. I'm going to lap the valves/seats with some course paste and a bit of elbow grease and see if the compression improves. But before I do I'd like to know if anyone thinks the hissing air past the valves on hand turning at TDC is normal?

I'm not going to crack the head and rebore a 120 and replace rings, but if I can get it running before that point then I'm all for it.

Appreciate some advice if anyone wants to chime in!

Cheers to all!

The Manual above is a must have, I have Shop Manual for our 1990 HR215SXA.