What is the crankcase breather separator/screen for?

[57pan]

I don't mean the gear-driven breather valve but the C-shaped separator and screen (OEM # 25275-36 and 25279-36) that goes in the cavity in the lower left corner of the gear case. It appears that this cavity is pretty isolated from everything else so what function is this screen actually performing?

The reason I'm asking is because I recently removed my cam cover and found that there is no separator/screen in there.

[fourthgear]

Its a foam or bubble separator that was needed for the older type oils with out anti foaming additives , some one posted that answer a while back. I always new it was a separator ,but I originally thought it was for just separating vapor from the oil return to the tank , so the foaming or bubbling separation ,makes sense too.

[57pan]

fourthgear,

Thanks for the quick reply... so I probably don't need to worry about putting one back in there, right?

[fourthgear]

Myself, I would put it in, they are not expensive and it belongs there , but that's your call and you haven't had any problems , have you?. I have a tappet screen missing from my 65 ( probably the previous owner or builder thought it didn't need it ), there will be one back in there when I assem. the motor. Maybe not the same thing but it belongs in there and it may have benefits we have no knowledge of .

[Panacea]

Dave,What's up inside the gearcover? Mike

[partshunt]

The way I always regarded the screen is that you need it to clean up the crancase breather air of all that oil. Its like an aircleaner and as the breather or base pressure air with all that oil in it from the con rods, rocker cover drain back etc. passes thru, the oil gets bassically "screened" and trapped into the scavange cavity where the oil then travels back to the tank. Without the screen, or installed wrong, your breather will slobber oil into the primary usually big time. This was all discussed in an earlier post where someone had too much breather oil into the primary case and big puddles under his ole hawg.. Screen was incorrectly installed. You always get some bubbles in the return oil and thats why the return is at the top of the tank to disperse the last of the bubbles that may still be in the return. There is a pic somewhere here in this forum of the screen properly installed. My suggestion is, install that screen.............Joe

[57pan]

Dave,What's up inside the gearcover? Mike

A while back I posted that I had replaced my alternator with a CycleElectric generator ( Replaced alternator with CycleElectric gen. ) One of the alternator mounting bolts had broken and the alt was rattling around on its remaining mounting bolt.

Well, after I got the generator on I could hear a noise inside the gear housing - kind of a knocking/clunking sound. I wasn't sure if it was a new noise or an old noise that had been masked by all the noise that the old alternator was making.

When I pulled the cam cover off I found that the idler gear that drives the gen had a tooth missing!! I couldn't find any pieces inside the gear housing so I pulled the oil pump. Sure enough, I could see that it had already passed thru the return side of the oil pump. A remnant of the broken tooth was embedded into one of the oil pump gears.

I got some used oil pump gears and a used idler gear but haven't got it all back together yet. And I still have to flush and clean the oil tank to make sure there's nothing in there.

My bike didn't have an oil filter when I got it and I was always of the opinion that if I changed the oil often a filter wasn't really necessary. But a filter in the return line would have given me added assurance in this case.