Re: CD-11’s compression issue

[fisherman6]

Did you check the bores of any of these while you had them apart? Bore gauge and measure, or check ring gap in the bore with the new rings, etc.? A slight taper in the cylinder can still benefit from new rings, but a badly worn cylinder that has become slightly out of round can actually get worse with new rings than it was with the old ones that were already worn into the irregularities of its bore. In that case the cylinder must be bored and oversized pistons and rings used.

With compression in the 30-35psi range I’d bet on the rings not sealing hardly at all. Hard for me to believe they will run at all with those compression numbers. My instinct tells me this is due to some out of roundness to the bores that is preventing proper sealing. Try a leak down test and see what kind of seal you have if anything at all. I’m with Frank that having those numbers on 4 different powerheads is absurd

I would try running one of the ones you got running in a tank for several hours and see if it starts to come up. If it comes up some I’d run it on a boat under load and varying speeds for a tank of fuel or so for a proper beak-in and see where that takes it. New rings in a well-worn bore can be kind of a gamble in my opinion. Often it will work but it ends up being a slow break in process.

-Ben

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