Yamaha advises not to crank with plug wires disconnected.
Normally a mechanic would connect a clip on switch at the starter relay to enable cranking. In that instance the ignition would be off. If you do turn on the ignition, pull the safety lanyard. That should kill all spark.
The compression numbers vary the engine model and horse power. In general for 2 strokes, compression could be between about 58 psi and 150 psi
A good guess an at typical number would be 100 psi. Most importantly cylinders should be within about 10% of each other keeping in mind that the two lower cylinders 5 and 6 have a slightly higher compression ratio and therefore potentially a slightly higher compression number.
The oil question is interesting. You can take a dry compression reading and then inject a few squirts of oil and take another reading. A large difference 'might' indicate stuck or binding rings. It could also mean a weak or broken ring. It's not a fool proof test. Remember that if you fogged your cylinders for winter storage, they will still have some oil in them
Normally a mechanic would connect a clip on switch at the starter relay to enable cranking. In that instance the ignition would be off. If you do turn on the ignition, pull the safety lanyard. That should kill all spark.
The compression numbers vary the engine model and horse power. In general for 2 strokes, compression could be between about 58 psi and 150 psi
A good guess an at typical number would be 100 psi. Most importantly cylinders should be within about 10% of each other keeping in mind that the two lower cylinders 5 and 6 have a slightly higher compression ratio and therefore potentially a slightly higher compression number.
The oil question is interesting. You can take a dry compression reading and then inject a few squirts of oil and take another reading. A large difference 'might' indicate stuck or binding rings. It could also mean a weak or broken ring. It's not a fool proof test. Remember that if you fogged your cylinders for winter storage, they will still have some oil in them