Oil pouring out of air cleaner box after ride.

Hello All.
Just returned from a good ride, pulled into shed and oil is pouring out of the air cleaner box. The bike ran really well on the ride but I'd noticed on previous rides that the oil warning indicator would come on pretty soon after topping up. As I have trouble seeing the oil level through the sight glass I'd put maybe half a litre in and be on my way. As it didn't leak oil or seem to blow much through the pipes I was a bit perplexed. On this last ride it seemed to use quite a bit of fuel too. The oil that poured out onto the floor smelled of fuel also.
I may have a float problem but how does the oil get back to the air intake?

 

Likely a float valve is stuck,allowing the carb to overflow into the airbox...then the fuel goes through the crankcase breather hose,fills the crankcase,and then backs up through the airbox. Check the oil for the smell of gas,and remove the oil filler cap. Have a look with a flashlight (not a lighter,as the crankcase may be potentially explosive),and see if the crank case is overfull. You can sometimes free a stuck float valve by tapping firmly on the carb bowl with a wooden hammer handle or something similar. This is a band-aid fix,you really should remedy the situation by cleaning and/or parts replacement. I would recommend,for your safety,that you not ride the bike until you have solved the problem. Let us know how you make out...

 

You want to get the oil/gas mixture drained ASAP before it kills your seals. Pull those carbs and get the floats to seal. Good Luck

 

This is a common, two-headed monster. First off, you have a float problem (could be as simple as a bit of crud) keeping one or more of your floats from shutting off, which is where the excess fuel is coming from.
The second part of the problem is your vacuum-operated petcock which SHOULD shut off (in the "ON" position) when the bike isn't running, may very well not be shutting off at all. When the bike is off, it should flow fuel only in the "PRI" position.

Danno is right, once the crankcase becomes overfilled with the fuel/oil mixture it pumps out the breather into the airbox.

Look on the bright side: After flushing everything with gasoline, you may be able to see thru the sight glass better... Seriously though, get that gas/oil mixture OUT of there it will not only mess with seals it will saturate the clutch; and get the problem fixed.

 

I like your style,Fitz! You said concisely what I could not. Not to mention that you really know your stuff!

 

Thanks for your help all.

I'll pull the carbs on the weekend and check the float operation. I've had the fuel/oil mix in the crankcase now for a few days so I hope I haven't stuffed anything up.

What puzzles me is why the oil warning indicator (I have the electronic instrument cluster) comes on after about 20km's. If the crankcase is filly up with fuel why would a low warning exist? Or does it sense overfilling also?

Also, does anyone run two fuel filters (in-line, apart the one out the petcock)?

 

The sensor may be bad. Its just a float thats in the oil pan. If the oil level drops the float switch sends a signal to the instrument cluster and trips the light.

 

The fuel filter in the petcock lets a lot of stuff through. Consensus on the site is to put on an inline filter ASAP after obtaining your bike.

 

Is it a constant that fuel will get into your crankcase if you leave the petcock in prime? I seem to remember doing that on more than one occasion, but I've never had a fuel-in-oil issue.

 

NEW OIL, NEW FILTER, new inline fuel filter.

always remember turn your petcock to ON not prime

if you have a service manual check to see how many quarts you need.

 

If your Needle valves are working properly fuel will be shut off when the bowl is full, petcock in the prime, on or res position.
Having the petcock in the on position cuts fuel to the carbs unless bike is running, just incase your needle valves are not so good.

 

Remember, though: Even PERFECTLY FUNCTIONING floats can pass a bit of crud or get hung for whatever reason, which is why bikes have had fuel shutoff valves (not always vacuum operated) since forever.

TheHound is right, as long as your floats are working correctly it shouldn't be an issue, but it's kind of like playing Russian roulette. Yamaha realized that humans forget, which is why we have the vacuum operated petcock in the first place.

It's a sinking feeling to walk out of the restaurant on a hot summer afternoon and see your bike sitting in the middle of an ever-widening pool of gasoline. (The Norton doesn't fill up the motor, it just pees out everywhere.) My point is that everyone forgets and if you forget at the wrong time... all hail the vacuum operated petcock.

 

Just a thought, if the oil sensor is just a float, and theres enough gas in the oil, couldn't it thin it out enough that the float stops floating? hence the light? pretty sure gas is way less dense than oil. Just a thought.