I've been doing the 12,000 mile maintenance on my 2014 C650GT and thought I'd share some of the things I've learned (and wish I knew before I started).
1. Oil Change
Changing the oil is pretty straightforward. I had to mail order the filter and 15w50 oil, but the rest was easy. The only hitch is the extra drain hole and the additional tube filter inside it. I used to have a Kymco scooter so I've seen that type of filter before. The trick is you have to be careful removing it and, especially, putting it back in or it could drop into the engine. When you do that, put a screwdriver or a socket extension or something like that into the tube and keep it in there until the tube is in place (the tube presses into in indent inside the engine). So that's my first tip.
2. Air Filter Change
The air filter is refreshingly easy to swap out. Just take off the upper right side panel, remove the filter cover, pop the old one out and pop in a new one in. No tips needed!
3. Rear Chain Drive
There is an inspection window in the side of the swinging arm you can use to check the chain tension. If it is loose, that is not a reason to buy a new chainset, replace the chain and socket, or even replace the chain. BMW sells chain rails you can use to adjust the tension. If you have the manual, they are easy to install. When I did mine I reused the swinging arm gasket, and I've had no leaks so far. The oil in there was really dirty but it is also really easy to change. There is a drain hole in the bottom of the swinging arm and a fill hole on top. My second tip is order yourself a set of chain rails and maybe a gasket just in case.
4. Variator
Doing maintenance on the belt, rollers and sliders is a pain because you to remove most of the panels on the right side of the bike plus to variator covers to access the inside of the variator. Be really careful because the tabs on the panels are easy to break and expensive to replace. You will need the 4" long torx sockets to put the cover back on and torque the bolts, as well as the variator tool BMW sells to keep things from moving, and a 33 mm socket to get the bolts off. Plus, if you have ever opened up a variator, there is something about the BMW variator that is different. You need to lubricate one of the splines with Unirex N3 grease. If there is something else besides that you can use, I don't know what it is; and if there is someone else besides BMW who sells the grease, I don't know who they are. So tip three is make sure you have the special grease (in addition to the tools, the belt, the rollers and the sliders) before you start taking the bike apart.
5. Gearbox
In addition to the chain drive and the variator, the scooter also has a gearbox that has 75w90 gear oil in it. The fill plug is not hard to access, but its way in there so you need a tube or something to squirt the oil in. The hard part is the drain; the exhaust expansion chamber blocks access to the drain plug. The manual says you have to take the right side panels off, drop the coolant tank and the radiator, and disconnect the center stand and the entire exhaust to access the drain plug. But I think you can get around that by disconnecting just the muffler (not the whole exhaust) and the center stand, which should allow the rest of the exhaust to drop down low enough to let you get to the drain plug. That's tip 4.
6. Spark Plugs
The spark plugs are behind the radiator, so you have to remove all the right side panels and drop coolant tank and the radiator to get to them. Tip 5 is think about doing the plugs when you do the variator. You don't want to take those panels apart any more than you have to.
