YAMAHA 3HP "MALTA" Low Compression ?

[abuonocoreca]

I checked my YAMAHA 6L5S017311 MALTA for compressioin. I get 4,5 Kg/cm2 warm engine, 4,8 Kg/cm2 cold engine. The unit is quite old, I don't extactly know it's life history.

Putting some engine oil inside the cylinder the compression reading (cold) rises to 9 Kg/cm2.

Which should be the correct reading ? Should I consider replacing the piston rings ?

Many thanks in advance

[rodbolt17]

I don't use the metric system, none of my gauges do either.
using oil to check rings is a waste of oil in a two stroke.
works,kinda on a 4 stroke cause they have valves.
do a leakdown test if you suspect ring leakage.

[abuonocoreca]

Thanks for the reply !

well 4,5Kg/cm2 is about 63PSI, and 9Kg/cm2 is about 125 PSI

I did the measurement as the manual cracking is very light, I don't feel the resistance pulling the rope I would expect.

What do you mean for leakdown test ?