Engine hole

[jonne123]

Is it normal to have hole under my engine sized like small fingernail head. where the engine halfs meet?

[Calum]

Yes that's normal

[jonne123]

Why it is there?

[Calum]

@jonne123 Probably to help split the cases when you rebuild them. But I honestly wouldn't know.

[SpookDog]

Sorry to rehash an old thread, but it’s a good question. It’s the first thing I wondered on when I first got my dt.
It’s an air expansion hole. There is a sizeable enough air void inside that is opposite where the hot coolant goes to the water pump. If it was closed the air would expand, into the crank or outwards if the crankcase seal failed...
I only worked it out when I split the cases...

[Stevie Wonder]

@SpookDog said in Engine hole:

Sorry to rehash an old thread, but it’s a good question. It’s the first thing I wondered on when I first got my dt.
It’s an air expansion hole. There is a sizeable enough air void inside that is opposite where the hot coolant goes to the water pump. If it was closed the air would expand, into the crank or outwards if the crankcase seal failed...
I only worked it out when I split the cases...

I’m so glad someone else did this
The exact same thing happened to me, one week in of ownership, cleaning the bike and inspecting underneath and then boom. A little hole had appeared in my crankcase and I certainly hadn’t been doing any enduro, confused the absolute life out of

[declan]

@Stevie-Wonder same with me lol

[Nottsbiker]

Someone at Yamaha put it there for a laugh so people for years would ask whats this hole for?