XL 760 Waverunner - No compression?

Question

99 waverunner has been running great until saturday afternoon. Was runnning across the lake and it died. Started right back up, but then died again and would not start back up. Got it back to the house and pulled the plugs. Plug out of the back cylinder was wet. Rolled the engine over to make sure nothing in cyclinder. Rolled fine, but just did not sound quite right to me. Gave it the "thumb over spark plug hole" compression test. Front cylinder popped thumb up = obvious good compression. Back cylinder = nothing.

What I can see of the piston looks good - not burnt or distorted.

What do you think?

Posible just broke reed valve or something more?

Answer 1

Possible burned piston.  It may be burned to the point where there is a hole burned through the piston.

Answer 2

Nope, you have a burnt/scored piston. The rings are stuck. Time for a top end job.

(think here, even if reeds were stuck, there would atmosphere in the cylinder which would compress some.)

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EDIT PART---------

Guess what came into my shop today? A 96 1100 with 20 lbs in #2 and #3! Pistons look good (via plug hole), but are burnt/scored and rings are siezed to the pistons. You will see a deformed spot on the edge of your suspect piston.

Answer 3

if you suspect a broken reed, you need to stop turning that crankshaft now, until you retrieve the pieces.  otherwise you'll turn a repairable engine into an anchor.

the cylinder head's got to come off anyway, just pull it & take a look, you have nothing to lose at this point.