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SOW1

wr400f is the fly wheel in a oil bath?

4 posts in this topic

when I removed the plugs on the flywheel cover to set at TDC oil comes out, is this normal?

thanks in advance

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just got off the phone with the local Yamaha shop and the service manager says it does indeed run in a oil bath.

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No...it is not an oil bather (also known as a wet sump). All our F motors are "dry sump" bikes that have a two stage oil pump. One half scavenges oil at a very high volume (and low pressure) and sends it up to the frame. The other stage of the pump takes the oil from the frame and sends it back thru the motor (high pressure & low volume).

Do a search for "YZF oiling system" I did an extensive write-up on the oiling systems about a year ago.

With that said, when the bike sets for a few hours / days (especially while on the side stand. Oil bleeds back down out of the frame into the engine. Hence why when you check it, it runs out the hole.

By the way, if you have a factory service manual, in one of the early pages it gives a real nice set of cutaway drawings showing the oil routing thru the engine. Stare at it for a while and you'll see the two systems.

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