Compression Checking on Yam 2-Stroke
I've been taught to take compression on a warm engine, with the plugs out and grounded.
A recent venture into Polaris 2-stroke jet skis, I learned that it is better to take compression on a STONE COLD ENGINE with the plugs IN the cylinders not being tested and the plugs grounded.
The engine will rotate faster and since cold you have a repeatable base line to establish norms.
I've tried this procedure and the above is true.
What does the Yamaha community have to suggest about this procedure ?
Also.....in jet skis "Piston Wash " is monitored. That's the areas around the outside of the piston top that is "washed" by the fuel. Viewed through the spark plug hole---it looks like small c's about the size of your fingernail, or so.
Not enough wash and the engine is running lean(hot), thus possible burning a hole in the piston.