Oil from carbs?

[silverbandit96]

I figured out that my bike was having trouble idling and bogging down because the air filter was incredibly dirty and something had been living in the airbox, no joke.  I haven't gotten a new one yet, so today I tried riding it w/o an air filter.  Seems the bike runs too lean and I need to put the choke on all the time for it to run right, but it doesn't cut out till like 9,000 now.  Anyways, a new filter is in the mail, but I realized when I came in today that oil had leaked all over the swing arm coilover and the rear tire.  Having motor oil on a smooth drag tire on a motorcycle is a really bad thing, I was starting to slide out whenever I got on it hard.  Anyways, it almost seemed that the oil was coming from the bottom of the air box, and when I took it apart there was oiled pooled up in there??  I looked around the engine and I oculdn't find any leaks, and the oil is above the transmission, so I'm not quite sure where its coming from.  It seems to leak only when its been running.  Any suggestions?

[Red01]

It will run too lean with no filter since it's now getting more air than it did when the filter was in there.

The oil in the airbox comes from the crankcase breather, that's why you only get oil in there when it's been running. That's normal, and why the airbox has a drain hose with a plug in it. You should periodically pull the plug and drain the oil. That's a good time to remove the filter and clean the inside of the airbox, too.

[elofdahl]

but I realized when I came in today that oil had leaked all over the swing arm coilover and the rear tire.

The engine “breather” hose is routed from the top engine cover to the upper part of the stock air box to allow the crankcase vapors to be combusted vs. introduced into the atmosphere.  Excess oil (minimal under normal circumstances) collects in the bottom of the air box where there is another capped hose.  At normal service intervals, the cap is to be removed and the excess oil captured and disposed of properly.  Many people (myself included) leave that cap off, and allow the occasional drop of oil to find its way to the street.

By your description of the oily mess on the rear suspension and tire it is likely that the crankcase was either over-filled with oil, or you have excessive “blow-by” (excessive crankcase pressure) which is allowing more than a normal amount of oil/vapor to be introduced into the air box.

Eddie

[Red01]

Many people (myself included) leave that cap off, and allow the occasional drop of oil to find its way to the street.

The problem with this is the open hose will allow the carbs to suck air up that hose, and it's end is close to the road where it'll pick up road grime.
Not a very good idea - and why they put the plug on there in the first place.

[elofdahl]

Many people (myself included) leave that cap off, and allow the occasional drop of oil to find its way to the street.

The problem with this is the open hose will allow the carbs to suck air up that hose.

Thanks for pointing that out Paul.  I just put the original plug back in place!