Help, hwat is this hole?

[the Norwegian]

Can someone tell me what those holes are for?
The lower one seems bottomless and it looks like my bike is leaking oil from that hole, i'm in a hurry because the three months ridingseason has started.

 

[DogBunny]

On the points side, those holes are threaded and hold the points plate in position. On this side they do nothing. Neither hole is bottomless, and even if they were, they wouldn't leak oil. Your leak is probably coming from the cam shaft seal, which is fairly common, and pretty easy to replace.

 

[Brian902]

If you look at this picture you will notice that the two end caps are the same and can be used on either side.

Extra screw holes are for points when used on the left side.

http://www.650motorcycles.com/XSignition.html

 

[XSLeo]

If the bottom hole is bottomless, some one put to long a screw in there and broke out the bottom. If it is broken out in the bottom. Get a set screw the right size to thread into the hole. It don't need to be too long maybe 5 mm or so. Coat with a good sealer, screw in the hole. So it is just a bit below flush with the head.
I agree with DogBunny, the seal on the cam is where the oil is leaking from.
Leo

 

[the Norwegian]

If the bottom hole is bottomless, some one put to long a screw in there and broke out the bottom. If it is broken out in the bottom. Get a set screw the right size to thread into the hole. It don't need to be too long maybe 5 mm or so. Coat with a good sealer, screw in the hole. So it is just a bit below flush with the head.
I agree with DogBunny, the seal on the cam is where the oil is leaking from.
Leo

Thanks for your replys, the camshaftseal is brand new and there is no leak around the camshaft.

When i looked at it, it was clear the oil came out of the lower hole. I was in doubt of where the leak actually where because i had to use the old o-ring and gasket behind the housing at the time i replaced the seal due to slow delivery of my new gasket kit. When i disassembled the housing from the head today there was no sign of a leak there.

I guess i have to try the setscrew then.

 

[5twins]

That hole should be blind and not go all the way through. If it did, it would go into the valve train area and, of course, oil would leak out. My guess is the old o-ring and gasket might be letting oil out from the bearing and it is exiting from around that hole, appearing to come from it but maybe not.

 

[DogBunny]

Neither hole is bottomless, and even if they were, they wouldn't leak oil. Your leak is probably coming from the cam shaft seal, which is fairly common, and pretty easy to replace.

I stand by what I said. Even if the hole is broken out in the bottom, it is not the source of your leak. Either your new seal is leaking, or your o-ring is missing or leaking, or your gasket is missing or leaking. You need all three.

 

[Uncle Bryan]

This might help. I just went out to the shop and pulled my housing off.
As you can see, all of the holes go straight through the housing.
The hole in question (and the other one at 11:00) are "blank" holes.
That is, they just butt into a blank surface of the head and are sealed by the gasket.
Even if the gasket isn't aligned correctly, the oil would still have to get past the o-ring.
By the way, the housing is about .272" (7mm) thick at those holes, if that helps.

 

[DogBunny]

I stand corrected, the holes do go all the way through, but the cause of the leak remains a missing or leaking, seal, o-ring or gasket.

Uncle Bryan, that bearing looks a little suspicious...

 

[Uncle Bryan]

I stand corrected, the holes do go all the way through, but the cause of the leak remains a missing or leaking, seal, o-ring or gasket.

Uncle Bryan, that bearing looks a little suspicious...

Gawd Damnit Bunny, I just put that cover back on. Looks like it's coming back off

Edit: Pulled the housing again, wiped off the bearing and it just had some crud on it. Bearing looks great.
While I had it off (again) I looked a little closer and the o-ring sits on top of the gasket. I assumed it sat in a groove but that's not the case. So yeah, at the very least, I would pull the advance unit and inspect the cam seal as I think that would be the path of least resistance for the oil to enter the housing.

 

[TwoManyXS1Bs]

Surprise! Here's a `70-71 head, right side. The hole is about 9/16" deep, threaded, and if drilled deeper, will NOT enter the cam oiling area...

 

[Uncle Bryan]

That's photo shopped And just when you think you got things figured out

 

[DogBunny]

Uncle Bryan, this metal band(?), which looks distorted to me, is what I found suspicious, but it's probably nothing. Anyways, I was curious enough that I pulled one of my cam covers. I don't have a band(?) like that around my cam bearing. But, I did find those threaded holes like in TwoManyXS1Bs picture, and I pulled the right side cover, so no points plate, and no need for those holes at all. That was a 78-79 engine according to the serial number. My guess is that Uncle Bryan's is a 1980 or later, and that when they went to the TCI they stopped drilling and tapping those holes in the head.

 

[TwoManyXS1Bs]

Could that line be a 'flash' artifact, like reflection from outer curve? Can see bearing #'s below line...

 

[5twins]

It's just oil pooled up at the bottom, that's all. All 5 holes are "blind", I just checked a motor I'm working on (but I already thought I knew this, turns out I did). Yes, I was wondering why Yamaha tapped the extra holes on the right side. Apparently they stopped doing that after '79? Someone at the factory must have missed the memo.

 

[DogBunny]

Oil, right, that was really deceiving.

 

[Uncle Bryan]

I would love to let this run for a bit because I really enjoy the "what's this?" threads.
But I don't want to hijack Norwegian's thread.
Today I learned that the machining changed on the heads and now I'm thinking that I don't have a clue what Norwegian's problem may be? Norwegian, do let us know what you find in there!

Yes my bike is a 1981 (good call there). What you are seeing in my pic is actually just a bit of very clean oil whose meniscus has allowed it to 'wick' up the I.D. of that bore, the bike is on the side stand so that's just the oils happy place

 

[5twins]

Unfortunately, oil's "happy place" seems to be on the outside of many of these motors, lol. I'm going to remember that one though. The next "I have an oil leak - help!!!" thread I see, that's what I'll tell them - that oil is just in it's "happy place", lol.