Hole? What hole? Should there be a hole?

[Salsa]

I have got my bike running and taken it out on the street now. It was a VERY short ride.
A few days later, I started it up and it would run until I gave it gas to take off.
Today, I started it again with the intention of adding gas and letting it run through to clear the gas that had been sitting in it. However, there was a bit of a knock sound so I killed it.
Got my dad out there and it would just turn over and not start. Even after adding some gas. Now, I'm supposed to be somewhere, but I'm posting first.
I was looking over my bike and videos looking for where to drain oil, the bike sat for two months and I'm having some issues. So figured this was one of the places to start and my next mission on this bike.
Then I found this:

. This is a different angle shot of it:

. If I stick my finger in it, I can feel nasty oil and junk built up there.

Salsa

 

[16VGTIDave]

Yeah, um. Okay. Did you look before sticking you finger in there? Good thing the bike wasn't running, or you may have drawn back a nub. The counter shaft sprocket is above that hole. With the chain. I'm fairly certain there is 30+ years of dirt and chain lube in there. Aren't vintage bikes fun?

 

[Salsa]

Yeah, um. Okay. Did you look before sticking you finger in there? Good thing the bike wasn't running, or you may have drawn back a nub. The counter shaft sprocket is above that hole. With the chain. I'm fairly certain there is 30+ years of dirt and chain lube in there. Aren't vintage bikes fun?

So should the hole be there?
Yes, I know not to put my finger in any running engine!

 

[Salsa]

So should the hole be there?
Yes, I know not to put my finger in any running engine!

So that should be the crank breather hole on my bike, it looks like.

 

[TazzTheJynx]

As for the engine knocking, make sure you're using the proper octane fuel. If it's too low the engine will knock. This goes for ALL vehicles, which is why you don't run unleaded in a vehicle that requires premium. Just as an example. Not sure what xs400 requires.

 

[Salsa]

As for the engine knocking, make sure you're using the proper octane fuel. If it's too low the engine will knock. This goes for ALL vehicles, which is why you don't run unleaded in a vehicle that requires premium. Just as an example. Not sure what xs400 requires.

Thanks. I will find out what it's suppose to have. I'm sure since the cap doesn't lock that it needs fresh fuel.

 

[drewpy]

Thanks. I will find out what it's suppose to have. I'm sure since the cap doesn't lock that it needs fresh fuel.

yamaha bikes were meant to run on unleaded since 1974.

Its the Ethanol fuel thats the issue now, absorbs water and sinks it to the bottom of the tank.

I use Millars dry fuel occasionally to counteract this

 

[16VGTIDave]

So that should be the crank breather hole on my bike, it looks like.

Nope. That is just a hole for crap the fall out of. The crankcase breather in on the other side of the engine with a rubber hole leading the the airbox.

 

[Salsa]

Well, I still do not have the bike running again yet. I pulled the tank and drained it, soaked the petcock, and put everything back together. I can drain the tank with it on Pri, but nothing drains, even when I try to start it, while on 'On.' So now I've pulled the carbs and a friend is cleaning them. Hoping that's as much as they'll need.