Bonneville America Forums Forums Technical Forums General Tech oil in the airbox

Bought an 02 bonneville for my wife. I love the bike except for one very irritating problem. The airbox keeps collecting oil which then drains out onto the floor when it is parked. I called the dealership and they said it was either an overfilled crankcase or a bad air oil separator. I checked the oil level and it looked good so I ordered and replaced the separator which is mounted to the end of the crankshaft and filled the case with 4 quarts of oil. I still have the same problem. Anybody got any suggestions?

Your bike uses about 3.7 quarts of oil after the initial fill at the factory unless you drained every drop from the motor. On oil changes you will use more than 3 less then 4 quarts generally speaking depending on your patience level for draining and letting it drip for days on end Also if you are changing oil from the side stand you are leaving oil in the sump because you are not straight up.

Drain it, put 3.5 quarts back in. Let sit for an hour and check the level. It will be between the two lines.

Have you cleared the crankcase breather? A clogged breather would allow the pressure to build up and force oil out some unsual places...like the air box.

Thanks for this info-

Where is this crankcase breather you're talking about?

At the back of the rear of the cylinder on top of the case is a black hose leading to the airbox , assuming it has not been replaced with an aftermarket breather , if it has , then just clean the thing up !