MP Proj. 001 Honda CL360 Part 7: valve leak test

Head: Pre-leak test

Although the last few posts about this build have probably been less than riveting, I have wanted to make sure I document the process as thoroughly as possible.  The mundane is often as important as the big moves that will be made, and this test is no exception.  I knew from the start that I would need new rings, after doing the compression test, and then confirmed it when I took the pistons out, and found that the oil rings were both cracked in half.

The next step was to try a “leak” test, by pouring WD-40 (other fluids are suggested too, like acetone or paint thinner) into the combustion chamber side, where the valve seats itself.  The goal is to see if the oil can get past the seal between valve and head – and if it does, a relapping of the valve seat is necessary.  Any leak would indicate loss of compression, and would decrease the amount of power the engine can generate.

Oil in the compression chambers

On this bike, there are 2 round depressions in the head, at the bottom is where the valves sit (2 in each depression, one intake, and 1 exhaust), with holes just to the side of the valves where the spark plugs poke through.  When the engine blocks are assembled, the piston head would be pushing up from the other side.  This is where the action happens, and the combustion occurs, making this little beast go.

The tedious procedures during a total rebuild can zap your enthusiasm, so I decided to clean the garage while leaving the oil to settle, and hopefully remain in the chamber.  After a few hours, the oil was still there, without any leaking through to the underside.  So far, so good.  Later today, we will see if it’s still a solid seal, if the oil sat tight overnight.

The next step will be to scrape off the old gaskets from the head.  I am a little nervous to push gasket pieces into the lower cases, so I will need to figure our a way to cover the openings.  Tomorrow the honing should be done – and I should know whether a new set of rings will give me the compression I am looking for.

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