Unknown hole in block 1979 gs850g

[LordJebus]

Hello I’m new to my 1979 gs850g but I cannot find any information on this problem. There is an approximately 3/8” hole in my engine block under and behind my stator cover (see attached photos) and it’s leaking oil when the engine is running. It seems like it’s meant to be there but I cannot figure what for or how to fix said oil leak. It’s awfully hard to access and the mirror used in the 3rd picture to peer into the hole is under an inch in diameter for further reference. Any and all information would be appreciated as I’m very motivated to get this bike back on the road.

[chuck hahn]

Drain hole for starter motor well. Usual suspect is the oring on the end of the motor has begun to leak.

number 6 here....................

https://www.partsoutlaw.com/oemparts/a/suz/50d40144f8700230d8b4e46d/starting-motor

[LordJebus]

Drain hole for starter motor well. Usual suspect is the oring on the end of the motor has begun to leak.

number 6 here....................

https://www.partsoutlaw.com/oemparts...starting-motor

I took off the starter cover and the starter bolts aren’t even there! This probably explains why it only kickstarts as well so thank you for your insight. I think I’ll have to check over all of the previous owners work for sure.

[chuck hahn]

yup... starter motor has wiggled itself out of the hole going to the idler gear. replace the oring since its already out

[Nessism]

Search "mystery hole" here on the forum, and be amazed that every possible question someone can have has already come up for discussion here!

[Brendan W]

There is a breather hose from the top of the secondary transmission case that is routed into the starter motor cavity.
Most likely the displaced starter motor is the problem but oil can come from the breather especially if the internal seals have started to fail and engine oil is finding it's way into the secondary bevel box. When this happens you will generally find the oil level in the secondary rising.

[bwringer]

LOL, the Mystery Hole strikes again!

Oil from the cam chain tensioner can also dump oil into this cavity and out the drain hole.

Do NOT plug the Mystery Hole, or the first time you ride in the rain you'll marinate your starter in a greasy soup of dirty water. Doesn't do it much good.

An example Mystery Hole from the top -- the blue tubing shows the inlet:


... and here's the outlet:

[Suzukian]

Shouldn't that be called "Mystery Drain"?

[Brendan W]

Shouldn't that be called "Mystery Drain"?

The mention of drain would take all the mystery out of it.
Much more fun having people wonder where their missing crankcase bolt has gone to

[bwringer]

More than once, people have plugged the Mystery Hole with JB Weld or similar. Weeks or months later, the space fills up and the problems begin.

Engines that have been sitting outside can end up with a blocked Mystery Hole due to assorted debris.

And when leaking oil finds its way to the Mystery Hole... sheer panic often ensues.

I started calling it the Mystery Hole many years ago, after the Mystery Hole roadside attraction in West Virginia:

https://www.roadsideamerica.com/story/10971