2000 yamaha115 4 stroke leak down test what % is acceptable

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what % is acceptable before service is required? what could cause the leak

 

[DangarStu]

The percentage varies greatly from tester to tester, so don't get caught up on the % too much. Here is a video I did on doing a leak down test on a Yamaha on the bench: https://youtu.be/dtETHoja8QI The think I like the most about leak down tests is being able to listen for where the leak is coming from - and really all you need for this is the compressed air, not the gauges.

The leak can be either the intake valves, the exhaust valves, the rings or the head gasket. These are the four main places they can leak from.

Stuart