Primary oil loss

[Mel Neff]

My '97 Dyna seems to be losing oil from the primary, and there is no evidence of a leak.  I have read that this could be caused by oil being sucked into the crankcase thru a bad seal or the stator wire clamp screws, but the seal is new and the screws are Loctited in.  Could this be a malfunction of the crankcase breathing system?  The service manual explains how the breathing works on the piston downstroke, thru the rocker boxes etc., but isn't clear about what happens on the upstroke when there is a vacuum.

[Hossamania]

Have you checked your motor oil or transmission oil to see if either is overfilled?
Also check your transmission vent for blockage.

[Mel Neff]

Yes, forgot to mention, motor oil is over full.

[Ohio HD]

Are you overfilling the primary> You just need enough to touch the bottom of the clutch basket when the bike is standing up right.

In any case, I don't see how it can't be the crank seal in some way. Was the spacer the seal rides on damaged, or have a groove worn into it?

[Mel Neff]

The primary was not overfilled, and that spacer is new.

[FSG]

but the seal is new

is it in the right way?

[Ohio HD]

As FSG said, it matters the direction it's put in. This video is a Shovel, but the same thing for Evo's.

[Mel Neff]

I believe I put it in the right way.  I'm careful about things like that.

[FSG]

I believe I put it in the right way.  I'm careful about things like that.

I'm sure your are, but it'd bee worth checking IMO

BTW  "the screws are Loctited in" 

did you clean out the holes and blow them out with an air nozzle and ball bladder inflator before putting the screws in ?

[Mel Neff]

I'm still wondering where the crankcase breathing air comes from on the piston upstroke, and whether that could be blocked somehow.

[Ohio HD]

I don't see how the venting system could cause oil to be pulled in from the primary. And if it were, it would be coming through the crankcase seal.

When system venting isn't functioning, you end up with pressure being expelled to the oil tank, and out through the head vents. It'll take the path of least resistance, so the crank seal isn't a point of pressure escape. If it were, it also wouldn't be pulling oil in.

If you want to test that head vents are working, feel that they are expelling light pressure with the motor running. Also you should not be able to blow back into the head when the motor is off. If you can, the flapper seals are worn out.

The vent timing is controlled by the rotatory valve inside the cam chest. It may be a plastic valve in 1997, I'm not sure. But as I said above, if that failed in some way, expelling gasses will take the path of least resistance.

In any event, oil coming from the primary no matter what the outside influence something in the motor has on it, would indicate that the seal is not functioning correctly. If it wasn't installed with a tool to press it in place without twisting the seal, you may end up with leaks around the seal casing.   

[JW113]

I'm still wondering where the crankcase breathing air comes from on the piston upstroke, and whether that could be blocked somehow.

It doesn't come from anywhere. That is, in a normal functioning motor. The whole point is that the pistons push air out the breather valves on the down stroke, and then draw a vacuum inside the crankcase on the way back up.

It is this vacuum that will cause the motor suck oil from the primary into the crankcase. Although it is possible this is happening at the stator screws, it's probably not likely. About the only reasonable way this can happen is past the sprocket shaft seal, OR the steel bearing insert has cracked loose in the left side case. This used to be quite common in Shovelheads (mine was) and 84-90 Evos. I think it is a lot (as in A LOT) less common in the '91+ Evos, but that doesn't mean it never happens.

Like it or not, you're going to have to take it apart and have a look. One thing you can do, after you have the compensator off, take the timing plug out and blow air into the crankcase (gently, don't seal it and pressurize it), and do a bubble test around the seal and area.

Just curious: why did you replace the seal in the first place? How long ago? And was this happening before you replaced the seal?

-JW

[Mel Neff]

I had it apart last fall to replace a bad stator connector.  At that time I suspected that oil was leaking in the OTHER direction, from crankcase to primary, but wasn't sure.  So I decided to replace it while I was in there.

[Dan89flstc]

As FSG said, it matters the direction it's put in. This video is a Shovel, but the same thing for Evo's.

I put the seal in the wrong way in my `89 Evo (back in 1996), it has not caused any problems. About 80,000 miles ago.

[Ohio HD]

I put the seal in the wrong way in my `89 Evo (back in 1996), it has not caused any problems. About 80,000 miles ago.

Spring towards the outer primary or towards the flywheels?

[flstffxe]

The 2 holes for the stator plug retaining clip are drilled straight through. If the screws are loose it will transfer oil between the crankcase & primary.

[jsachs1]

I've had engines, even some NEW crate engines come in with that seal in either direction.   Never a problem. Check the breather gear for missing teeth, or incorrect timing.
John

[Mel Neff]

I have it apart, and the seal was in the right way (spring toward primary).  I'll put in a new one, and see what happens.

[kd]

I have it apart, and the seal was in the right way (spring toward primary).  I'll put in a new one, and see what happens.

Was the lip still sharp and tight to the spacer?  Post a pic if you can and the spacer seal surface or when you get it out.

[JW113]

No bubble test?

-JW

[Mel Neff]

No bubble test?

-JW

Oops, forgot to do the bubble test. Too late now.

[Mel Neff]

If anyone is still reading this:  The operation was successful!  800 miles with the new seal, and no primary oil loss. 

[Chippitt68]

Good news.

[nibroc]

thanks for the update