BMW R1200R R1150R/T F800 K1200R R1100R/T R1250R RnineT Message Board

Hey, guys.

For the past 3 / 4 tanks, I've been averaging pretty miserable gas mileage - about 33mpg. Most of my trips are short (3-4 miles) on the highway, too and from work. I ride more aggressively than is necessary, usually cruising at about 80mph. I've kept the oil topped off (around 1/3rd - 1/2 way up the glass window), and the tire pressure is good. When I took the bike in for its 24k maintenance (about 2k miles ago), the mechanic mentioned that my final drive was leaking oil, and that it was something that should be addressed (but hasn't yet). Could the final drive leaking be causing my weak gas mileage? Any suggestions for troubleshooting the problem?

Thanks!

You should be getting around 40/43 mpg...33mpg is WAY low.
Also, unless your FD is binding nastily (and it would smell and feel VERY hot and make noises!), it should not affect your gas mileage at all. If your motor is in PROPER tune and your air filter not clogged this bad mileage would require some detective work. One thought, are you dragging your rear brake!?

Make sure that it is not your output shaft seal that's weeping....your tech should be able tell if it's that by looking up the tunnel and seeing if it is running down. The FD seal is rarely fatal and a PITA job....now, if you only have a tablespoon or so of oil that goops out between oil changes, I wouldn't bother to do the job.
Just could just undo the boot clamp, drain out the leakage, clean it out and top up your FD if needed.

Not sure if you are handy with a wrench, but it's not a hard job to check the boot, drain it and top up the FD if needed. You could check it every 1k miles to make sure it hasn't terminally failed (rare!) or at every 3k engine oil change and, if only a couple of tbsps leaks out, it would cost you pennies to top it up with 75w90 vs mucho dinero to fix the seal. YPYMAYTYC !!!

You should be getting around 40/43 mpg...

Really?

Wow, I've always gotten 50+ for combo driving. I must be living right.

Well, I've gotten 48 being sensible and all that but, given my location and riding style, I get low 40's

MPG and final drive seal leaks are unrelated...

I would be checking for binding brakes, especially if you have ABS fitted, those things have a mind of their own

Go for a 10 minute ride on a straight road without hitting the brakes, jump off and feel the brake disks

they should be cold...

I'm non-ABS, but I'll take a look at the air filter and rotors, see what I find... what ever happened to self-adjusting disc brakes?

Also - I just replaced the clutch cable about 400 miles ago, but haven't yet had to let it out... could a loose clutch cable affect MPG?

thanks for the responses, guys!

Oxygen sensor?

Try removing the fuse for Motronic (it may be #5), turn key to on position and turn throttle to full on/ off twice. Turn off key and reinsert fuse.

Remove the 1st relay for fuel mapping (actually it is just a jumper) and jump terminals 30, 87a and 87 (stock mapping).

I forget how to but you can also test the O2 sensor via resistance I think. If bad, go to McAuto parts w/ your old one in hand and insist it came off any 1990ish accord, camry...etc. If the treads are the same and it has 4 wires (must have 4 wires), buy it and splice away. You may luck out and have the connector attached.

You may also have a CO pot which acts as your fuel mixture screw in place of the fuel map jumper (Located RR of bike reached from close to where passenger right thigh/butt would be. I think clockwise is lean but not certain.). I wouldn't lean the mixture without some sort of exhaust sniffer.

If everything fails pump tires to 1000000000psi and call it character.