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Air/oil separator??

Discussion in 'Technical and Troubleshooting Torque' started by ANDO, Nov 25, 2005.

  1. :? well I have a honda CB250 95' (yea yea...don't laugh)

    Now to the prob....well not a problem yet.

    Now I needed to change my air cleaner - no prob, but when I was down there having a bit of a sus of the working's of this thing I noticed a little "black box" with what looked like oil and dust on it.

    Strange I thought as the bike's motor and carbs and all are rether cleen and this stood out like dog's ba....yea so I cleaned a bit of this oil/dust of and there is two screws holding the lid of this "black box", one at the front and another on the other side but up the back......am i making sence still?

    So coz there is only two bolts that hold it on this allows a gap between the lid and the bottom - hence where all the crap is coming from.

    Now I found out today (after a few weeks) that this is the air/oil separator, now what will it do if air is getting in and or out???? (it doesn't seem to do anything bad at the moment)

    thanx :)
  2. BUMP.

  3. I believe the air/oil separator is a carry-over from US emission regs. It just prevents oil being burned in the mixture and releasing naughty hydrocarbons into the atmosphere. You could probably remove it completely and it would make no real difference to anything. (Apologies to any lurking tree-huggers)
  4. Yeah most bikes just plumb there crank case breather straight into the bottom of the air box.

    The carbon filter thing is ugly and probaly clogs up. get rid of it if you can
  5. thanx guy's,
    you say get rid of it, but what would i put back on there?
    The air filtter eliment is like cardboard - like a pod filter but stock??

    thanx again :)
  6. Basically what you are looking at doing is removing the can and all hoses. You then need to plumb from the crank case breather hole to the air box.

    all other holes created be the removal need to be pluged.

    Keep in mind we are making a bit of an assumption about what this thing is. You don't see many Australian bikes with these things on. A photo would be handy.

    Can someone else with a cb confirm that is what we a tlking about.
  7. Yea thats a good point - it might not even be what im saing it is, will get a pick at lunch (wont be the best) but yea can anyone with a cb250 have a look at what it is?
  8. Well, cant take a pic - bat flattery :oops:

    I will try and google it :?
  9. Here an article about removing the smog canister from a xr650L.

    It might give you an idea about what yours is and about what needs to be done to get rid of it.
  10. OK. I think it's just a water trap. Lets oil back into the engine, without letting water in
  11. yea that sound wright, It also has an overflow thing that sits nexto the crankcase breather (well there are two hoses that come out from the bottem, one with a cap one without) so yea would make sence.

    So does it matter if it's not air tight?

    ps sorry about spelling, and thanx for the help :)
  12. I'm not sure how it works, so I don't know. Chances are it’s not working properly, because of the age.

    Don't worry about the spelling. Only people who need to prove their "intelligence" criticise other people about their spelling.
  13. thanx ibast,
    thanx for all the help - it's not doing anything at the moment, so I will just let it go for now. I will pull it of and have a better look when I clean the carbs (very over due).

    I like it here I might just hang around (might learn a thing or a million) ;)
  14. Just a thought is it the main crankcase breather ???

    If you take it off and shake it, and it rattles it would contain a ball which allows the the crankcase to vent to the airbox so if rings are shot any by pass or blow back is able to vent to the airbox.

    Just a quick thing to check is there a vent line running from the top of the rocker box back to the airbox ??

  15. Could be. I'm used to them on top of the rocker cover, but Honda may do them off the crank case and use a check vavle.

    In which case you wouldn't want any water getting in and you would want the check valve to work properly
  16. with all my laverdas they sit in the crankcase and vent out near the swing arm very enviromentally unfriendly so allways an excuse for a rebuild
  17. Really. My old SF3 used to vent out of the top of the rocker cover and was just a long tube that vented over the battery
  18. Sorry my triple does have the vent in the crankcase and the twin sf 750 they do sit in the head

    I have tended to concentrate on my triple in the past so the twins still catch me out from time to time.

    Its nearly finished now its taken 10 years to almost finish it its a 750 SFC replica now with the frame mods to run the two into one laydown shocks etc it was a basket case when i got it still fidling with the crank and cam at the moment and the balance weights it might end up a 76 deg crank can then take out approx 2 kilo off crank.

    Do you still have the SF3 iblast
  19. Nah sold it about 9 months ago. I needed something for getting to work and the old girl was too tepremental and viby.

    It had a sfc regrind in it.

    I did a rebuild but never got around to spending that last bit of cash and time that really tidy up bikes like that.

    Lot's of character though