My trusted mechanic sez that I have been overfilling my oil and this is causing my leaks. Not wanting to disagree (he drank harley oil outta da bottle while bouncing on his grandads WW1 relic. But does this happen? I thought the oil tank was a resovoir(sp) and you really couldnt overfill if ya left some room in it. If it does what leaks could it cause? smoke? pushrod? pipes Thanks for listening Dusty

 

I do not think that is correct info. But let me say I am talking about a 1974 and earlier here, although a 1979 should have the same thing. You are correct, the oil tank is nothing but a reservoir. There is zero pressure in the tank.
Inside there are two 'vent pipes' that end up near the top of the tank. One is a vent for the engine crankcase and the other is the return oil line. You want to keep the oil level below the top of these tubes, but they are very high up in the tank as I said.
I do not understand how too high oil level would cause the bike to leak, as long as the vent and return oil holes are open. More than likely the leaks are due to the fact that the machine is a Sportster. Just my 2 cents..........pg

 

There is a crankcase vent line that goes to the oil tank. If you manage to fill the tank enough to cover the outlet of the vent, it could cause you some problems, mostly oil blowing out of the lower breather down by the generator if the 79's still had that.