Gas tank question

I have a '79 R65. I never really liked the shape of the tank so I want to change it, preferably something with a higher capacity. What tank will fit from other models without any major modifications? Here's a picture of my bike.

I can't seem to find much in RealOEM that suggests it would fit. R65 was always a bit of an odd duck and didn't necessarily share parts with its other cousins. What capacity does your tank have now? Specs suggests that is around 5.8 gallons. That seems like a good amount. My /7 is only 6.3 gallons and it does OK for me on range.

The R65 tanks (5.8 gal) are unique to that model, as is the tank used on the R80ST, R80G/S, and R65GS (5.1 gal) from that vintage. Some ST owners here in the west installed R65 tanks in search of a bit more range, or opted for tanks from the P-D kit (8+ gal) or the R100GS tanks (6.3 gal). However, those tank swaps usually involved reworking or swapping seats or just living with a poor fit between seat and tank.

Since the R65 is such a unique bike I suspect you’ll run into the same seat/tank issues. You may be better off to start searching parter sites or BMW buy/sell forums for a good set of the Luftmeister saddle tanks that mounted in place of the side covers. 2 tanks, about 1gal each, gave a nice range boost. If you find a set, Snowbum’s website has information on correctly plumbing in the tanks.

Another option is a simple fuel cell like the ones from RCI, JAZ, etc. or a RotoPax container mounted on the luggage rack.

Best,
DeVern