Changing the gear oil on my Honda Ninety

My instructions are to refill the gear oil thru the drain outlet. When oil seeps from the oil level puka replace the plug. When oil seeps from the vent, replace the plug. Then remove the oil pump filler tube and replace the drain plug without losing more than one ounce of oil. Mission Impossible. After losing more than an ounce of oil why can't the lost oil be replaced thru the vent or oil level outlet? Thanks for all responses. Regards, Ronnie.

It is the way it has been done for some 60+ years.---------Add the lost oil at the vent if you must.------------It will take some time while air escapes.

Tilt the motor up before you remove the gearlube pump from the lower hole. It will keep you from standing on your head and also give you a little more control and ability to use two hands. I usually just stick my finger in the hole until I finish dropping the plug.

Just as a side note for others who may be wondering about the two plug holes at the top. That only applies to the BF75 and BF90 made in 1995 and 1996 that used the Mercury gearcases. Those are the only Hondas that had the two gear lube holes at the top. The vent is not to be confused with the wash hole in other motors, used for flushing the engine.

Mike

You're working off the old "finger over the straw" method of drinking a coke. If you replace the fill plug when the oil starts coming out of the upper hole, it shouldn't want to "gush" back out the drain. This is, of course, if the gear case is "air tight". Even if it is, you will get some leakage and you want to be prepared and QUICK. You can top off if you want after tightening the drain screw. It's just a messy job at it's best sometimes.

If you are doing this "messy job" because of a leak or water contamination of the gear oil then you would be well served in getting the gear case leak checked. It has to be pressurized and then tested to hold a slight vacuum to make sure all of the seals are in good enough shape to keep the lube in and the water out.

Thank you, Gents, for your timely advice. No water contamination. Just changing out the old many years oil for new. Ronnie.

OUCH! Lower gear oil should be changed annually as a minimum. I change it on my 225 every 100 hours.