Identifying an oil leak(s). Leaking only when the engine is running?

Its been a long time

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Had the bike running (rough) for about 5 minutes this afternoon. Started about 3rd kick, running very rough and hesitates to take any throttle at all.

But, the engine having been completely oil tight standing for several months leaks as soon as the engine starts. The clutch pushrod, gearbox sprocket, crankshaft, kickstart oil seals are all good. The sump plate gasket is good in any case it's not under any pressure. The two drain plugs are good, new annealed copper washers.

A picture from under the bike shows three dew drops of oil, and a dew drop on the bottom of the right lower frame rail. It seems oil is leaking only under pressure and from several places. But I'm flummoxed where the leak(s) is/are from?

Please see picture below to see what I mean. The chrome acorn nuts were my #1 suspect. But they look good.

Suggestions where to look please? It should be obvious, but it isn't.

IMG20240605155127.jpg
 
Lay a paper towel in the suspect area and hold it there,
might give you a trail as it absorbs to see where it's coming from. :shrug:
That's part of the problem. There's four seperate dew drops of oil. Three on the engine where there's no apparent leak point. And one on the frame. I don't think any of the dew drops are actually leak points?
 
Suggestions where to look please? It should be obvious, but it isn't.
I’ll suggest (guess) twice cuz I’m coffeed up.
1st - starter seal.
2nd - that gear cover under the drive sprocket
 

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Sorry to refer back to mine again, but rough running and a refusal to take throttle turned out to be a tiny tear in the carb diaphragm. Not visible until slide and diaphragm were held up to the light and gently stretched.

Good luck finding the oil leak(s).
Thanks, I appreciate the input. My thoughts are butterfly shaft seals and/or diaphragms. I tried my hardest to see diaphragm issues. So I won't discount it.
 
I’ll suggest (guess) twice cuz I’m coffeed up.
1st - starter seal.
2nd - that gear cover under the drive sprocket
Thanks. I'll be poking around there for sure when I do the starter grinding fix. My initial response is that those two suggestions are too far to the rear of the engine? I can't rule it out though.
 
Spaghettis at the wall, how your breather tube? Could it be mist collecting?
The breather tubes have spring clips and as a secondary measure have cable ties pulled tight around them. Still connected to the stock air boxes. I will double check for oil running down there though.The engine after 5 minutes running is pretty much cold, not much oil mist?
 
Check around the oil delivery tube at the front of the engine too.
Two connections there, one into the block and then the tube to that connector. Also the two bolts and their threaded chrome counterpart that hold the front cam chain guide. A quick wipe around can eliminate or confirm those in a minute.
 
Check around the oil delivery tube at the front of the engine too.
Two connections there, one into the block and then the tube to that connector. Also the two bolts and their threaded chrome counterpart that hold the front cam chain guide. A quick wipe around can eliminate or confirm those in a minute.
Thanks, that's a quick check. I'll do that.
 
OK. After thinking about this and reading the responses above, I've had another careful look around.

There's no oil dripping from the front of the engine. That's fine and ruled out.

The two main gaskets that I haven't replaced in this recommissioning job are the one covering the starter motor gears below the rear sprocket. The other one is the right side engine cover gasket. Both are showing dew drops from the gasket at the lower edge.

I guess these are 47 year old gaskets and starting up for the first time in over a decade has caused them both to leak. They are now leaking on a cold engine. They didn't do that before today. So, I'm replacing the right side engine cover gasket anyway to fix the starter grinding. I'll now do the start motor gear cover gasket too. Makes sense when you think about it.

The starter motor itself is showing no sign of oil leaking.

Pictures -

IMG20240605185300.jpg


IMG20240605185404.jpg


IMG20240605185724.jpg
 
Small oil leaks are notoriously hard to track. One old trick is a light dusting of baby powder, corn starch or the like on suspect areas. Combined with a good light this might help track it down. Best of luck.
This is what I was going to suggest cause its easy to hose down and clean off when your done.
you can put your phone under the bike and run video to capture as your starting it up before you can get your head under there.
 
Hopefully found the leaks . . .
I have definitely found two leaks. One left side, one right side. I am doing the right side gasket anyway as soon as the parts get here. I just need to order a gasket now for the starter gear cover. Change that as well.

We'll then see if I've got an oil tight motor at last :laugh:
 
I have definitely found two leaks. One left side, one right side. I am doing the right side gasket anyway as soon as the parts get here. I just need to order a gasket now for the starter gear cover. Change that as well.

We'll then see if I've got an oil tight motor at last :laugh:
Gear cover gasket on it's way.
 
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