What is the oil seperator!?

[jonathacvb]

HI, first I apologize if this is posted in the wrong place. I seem to be unable to create a new topic in the more specific areas.

I have a 'new-to-me' xs1100sg. It's having some issues with idling poorly and backfiring while riding. The carbs were rebuilt by the previous owner and so before I decided clean up a few other things first.

I tore apart the airbox and tried to clean it up a bit and put it back together. While doing so I came across this part (pictured below) which apparently is labeled as an 'oil separator' in a parts diagram. Now I have a pretty good mind for problem-solving but for the life of me I cannot figure out how this thing works. During the process I actually busted it up pretty good. Thankfully, the previous owner sold me bike with salvage from another and so I had an extra oil separator which I was able to used.

Is someone able to explain what this part does and how it works? There appears to be no information about it anywhere as far as I could tell.

Thanks in advance

[Schming]

The single port receives blow by gases from the crankcase. The other 4 ports and curved tubes head into the intake venturi. It is designed to eliminate crankcase fumes from entering the atmosphere.

[jonathacvb]

Ahh, ok. I will have to look closer but I don’t think I had a hose running from the crankcase to the port. Would that affect performance at all?

[Schming]

Not really, but the port on the top rear of the crankcase should not be plugged, it needs to breathe whether to a filter or to the stock location.

[Tonyxs11]

Ahh, ok. I will have to look closer but I don’t think I had a hose running from the crankcase to the port. Would that affect performance at all?

it comes from the head, over the carbs to the airbox.

[Schming]

it comes from the head, over the carbs to the airbox.

Not on an XS11

[jonathacvb]

Thanks for the input, I believe I found the hose. I will send a picture later today.

But this begs a question regarding blow-by… my previous experiences let me to believe that blow-by in the crank case is always a bad thing usually caused by a bad seal in the piston. But based on this conversation perhaps that is not the case.. what am I missing here?

[Tonyxs11]

Not on an XS11

DOH brain fart !!!! just been working on my GSX1100 and that does come from the head. must of had that picture in my head but yeah it comes from the top of the crankcase on the XS

[Tonyxs11]

Thanks for the input, I believe I found the hose. I will send a picture later today.

But this begs a question regarding blow-by… my previous experiences let me to believe that blow-by in the crank case is always a bad thing usually caused by a bad seal in the piston. But based on this conversation perhaps that is not the case.. what am I missing here?

the idea is, any vented gasses from the crankcase gets sucked into the combustion chamber and burned instead of out to the atmosphere.

[skids]

I took that "plumbing" out of the airbox. Do you really think that crankcase mist will keep the finicky carburetors clean? In fact, I took the vent hose off of the airbox, plugged the airbox and reduced the fat hose from the crankcase to install a crank breather filter. I guess I am an EPA offender, but a poorly running bike does the emissions no good either.

[jonathacvb]

Thanks for input guys! I chose to keep mine in because, as a novice, I wasn't clear on the consequences of taking it out. I appreciate the comments.. learning as I go here