Shovelhead primary oil circulation/venting issue

[realgone]

Picked up a janky shovelhead chopper this spring, built with a claw hammer and a blowtorch, ridden hard and put away wet.

I had the primary off for some repairs, and now that it's all back together I have a problem with oil puking out the inner primary when it's running. Hard to tell, but I think it's being pushed out of the hole for the fxe shifter arm.

The bike is running a wet chain primary, no chain oiler.

The three main oil lines from the oil tank to the oil pump are connected the way you'd expect:
Feed line from the tank going to the upper outer inlet on the pump
Return line from the oil tank going to the upper inner outlet on the pump.
Vent line from above the oil pump going to the oil tank.
Those are the only lines connected to the pump.


The vent line that is to the left of the oil pump on the case if you're looking at the motor from the back is connected to the inner primary.

That's it for oil lines and vent lines. No T connectors or anything else connected.

Should the vent line that is currently connected to the primary be vented to atmosphere? Or connected with a T to the oil tank/pump vent line?

Is it pumping out oil because of the way it's connected, or do I have a sumping problem? or both?

I can't see why it is connected the way that it is, but this is new territory to me.

[JBinNC]

I'm gonna try to sort this out, but some of the information provided is contradictory.

As I understand it, you are running what most people call a "sealed" or "isolated' primary, where the primary chain oiling from the oil pump has been eliminated. If that is the case, there should be NO oil lines connected to the primary. The primary does need to be vented, and most people leave the original primary chain oiler fitting open for that purpose. The FX through the primary shift shaft hole needs to be plugged because it is big enough for oil to splash out, or water to enter.

The oil volume in an isolated four-speed primary can be only 6 or 8 oz. or the clutch will be drowned in oil and won't function well.

As far as the oil line fittings on the CASE, inboard of the oil pump, there are two. One is just inboard of the pump, and hard to see, and is 1/8 NPT. That is the oil return line from the bottom of the primary, and with an isolated primary, it must be blocked off.
The other fitting is 1/4 NPT, and is the crankcase breather line. It should be open to the atmosphere. On the original assembly, it was routed around the back of the transmission and pointed at the chain, to provide oil to the final drive chain. On the newer shovels, '79 or so, and up, it was routed to the back of the air cleaner. I usually run that vent line to the right rear corner of the frame, and use spray chain lube on the chain, as that is cleaner.

My suspicion is that you have connected the crankcase breather line to the inner primary, and that is your problem.

Jim

[Dragstews]

If indeed you're running the primary sealed (As in the Evo design) there is this gizmo that helps the clutch contend with the oil ...





Primary baffle plate helps keep oil out of clutch pack.
VT No 12-1519

[realgone]

Thanks for the replies.

The vent line that is currently connected to the primary for some reason. Could I tie that vent line from the case in to the vent line that goes to the oil tank? I'm wondering if that would help with any drips on the ground.

[JBinNC]

Thanks for the replies.

The vent line that is currently connected to the primary for some reason. Could I tie that vent line from the case in to the vent line that goes to the oil tank? I'm wondering if that would help with any drips on the ground.

The so-called vent line from the cam chest to the oil tank is not really a "vent." What it does is equalize the pressure/ vacuum in the cam chest and the oil tank. Without it, the oil will not circulate properly.

The crankcase vent line that comes out of the back of the case is the vent to atmosphere for the entire system and is NEEDED unless you want oil leaks from hell all over your motor.

ALL H-D motors are set up this way. The location of the crankcase vent is really the only difference between the different models.

Jim