working on a 91 ultra and it was leaking from rear cylinder base gasket but its also spewing oil from what looks like a vent hose that's coming out of the crankcase. its located in the rear center of the cases. what will cause this? thanks

 

Many gravity feed oil tanks drain themselves into the crankcase when out of service for any length of time.
Such an over abundance of oil cannot be physically scavanged back to the oil bag at that point, and will snot itself out on the ground.
Shy of that, it would be a sheared return oil pump drive shaft key, but you can rule that out if once running, pull the oil filler plug and witness if you have oil returning to the tank.
Scott

 

Thanks for the reply. Bike has been sitting.if I drain oil and do a oil change it might correct the problem then right?

 

No.
It'll need tp expell the excess, unless there is a crankcase drain on that.(which I am almost positive there is not)
Scott

 

Ok so just run it and it should empty out

 

got a manual and it looks like the line leaking oil is supposed to go into the air filter.it is just hanging down.has a s&s filter assy and theres no place for it.

 

Sounds like the breather hose. If the motor has a bunch of oil in it because of the check valve leaking by and a gravity feed oil tank, as Scott suggests, oil will blow out the vent when the engine fires until it has expelled all the excess oil from the crankcase. Check the oil level in the tank; make sure it has some in it. You might get a rough idea how much oil has leaked by the pump check valve from how low the tank level is, if that's what's happening.

You should be all right putting the end of the vent line in a catch can and starting the engine.

Also as Scott said, leave the cap off the oil tank and look in there with a flashlight while the engine is running: you should see oil returning to the tank.