Vespa Gearbox Oil Change
A two stroke engine lubricates itself in two separate ways. The gearbox, clutch, and drive is lubricated by standard gearbox oil. There is no oil pump but instead the gears running in the oil manage to pass enough oil around the gearbox to lubricate it properly. Gearbox oil in a Vespa scooter should be changed about every 3000 miles with new SAE 80 gear oil, which is the same as SAE 30 motor oil. For some reason oil manufacturers have different viscosity definitions for motor oil vs. gear oil. This is a constant cause of confusion when buying transmission oil for your scooter. If in doubt remember that oil for car engines is crankcase oil and oil specifically for scooter transmissions is gear oil.. Below are directions for most large frame Vespas. These instructions generally apply to small frames Vespas as well but the filler and drain holes are in different locations.
Tools - You will need:
It is a good idea to run the bike around for a while to get the oil hot as it will flow much more easily. Place the bike on its kick stand on level ground and look underneath the right hand side of the engine. You'll see a small bolt that (if it is not covered in grime) should have OLIO printed on the head. Below is a shot of the oil drain bolt location on a large frame.
Place an oil drain pan below the bolt and loosen it allowing the oil to drain. Be careful not to lose the small sealing washer around the outer rim as this can be reused if necessary although it is best if replaced. Once the oil plug is removed the oil will flow out of the crankcase into the oil pan below.
Once all the oil has drained out, refit the oil drain plug, but only turn it about 1/2 to 1 turn past finger tight. Once the oil has drained refit the drain plug with a new felt or brass sealing washer. DO NOT tighten more than about a 1/2 to 3/4 of a turn more than hand tight. The small diameter and soft aluminum casing make it easy to strip the threads. If you find that the threads are stripped or you strip them yourself I have had success with using white plumbers tape around the threads. It can be bought at any hardware store and is basically a very thin plastic tape that plumbers use to seal threads when connecting gas or water lines. Wrap a 2" length around the threads and carefully tighten it in place.
Find the oil filler hole which is just to the rear and slightly below the gear selector box. Remove the slotted bolt with a large screwdriver. The new oil goes in this hole and needs to be filled up to the filler hole level when the bike is on the stand on level ground. I use an attachment tube which screws on to a standard quart of oil. These are available at most auto parts stores.
The shot below shows the oil just at the filler hole level, (and a little dribbling out. Refit the oil filler screw/bolt and double check you are not getting any leaks from the oil drain plug below. Auto parts stores will take your old oil for recycling and should not charge you for it. Most recycling centers will take it for no charge and it really does mess things up if you just dump it.
The oil drain hole is located just under the lowest point of the casing on a small frame Vespa.
The filler hole is located just below the rear shock mount on a small frame.
Here is a video on how to complete an oil change on a vingate Vespa. The video is a bit dated but it has good ideas like how to use a condiment bottle to fill the oil (we prefer a more narrow tip). Finally this video contains advice and images on how to evaluate your oil to see if it contains gas, water, or pieces of your clutch cork. All of these are signs of a larger issue you should address sooner rather than later.