Ok so ive run 2 tanks of gas through the gs since the sprockets and tires were swapped out.  99% has been 2 up riding.  14/45 sprockets and 160/60-17 rear 120/60-17 front.  mileage is averaging 52.5 MPG  for the feeling i get on the bike now i dont mind the 10mpg i lost.  just figured i would give an update since i fueled up today and figured maybe someone would like to know what the mileage is from stock gears.

when I went from stock to a 42 rear, I didn't see any mileage difference. when I went to the 14 front, I lost like 5mpg

Need to look into mine and see if any mods were done by PO's that would reduce gas mileage. It runs great but wouldn't get 50 miles per gallon if it coasted downhill with the engine off for 25 miles first.

I'm betting riding style makes a much bigger difference than small changes in the sprocket size. Here's more than a year's worth of data for my bike and you can see that 10 MPG is not that significant of a variation over a couple of tanks of gas:

http://www.fuelly.com/driver/fredzyda/gs500e

I've had variations of nearly 20 mpg and I haven't changed the bike in any way that would effect mileage. The standard deviation of the mileage for my bike is nearly 5 mpg...

Quote from: XealotX on May 08, 2009, 02:59:43 PM
Need to look into mine and see if any mods were done by PO's that would reduce gas mileage. It runs great but wouldn't get 50 miles per gallon if it coasted downhill with the engine off for 25 miles first.

Have you checked exhaust clearance, and/or valve clearance in general? Someone was having mysterious poor milage and it turned out to be exhaust valves way out, IIRC. I suppose poor compression might have a similar effect?

One other non-performance and non-driving habit (25 mpg is remarkably low even for a GS500 race bike, from what I recall seeing around here, so neither seems like a good explanation....) issue might be dragging brakes (are they hot if you go for a ride with little brake usage? Can you coast downhill, even if you don't have a 25 mile downhill handy?)

50 mpg seems really good with those sprockets. Riding around town very conservatively I got 50 mpg out of my last tank with about 50% being two-up riding. I basically rode all of the 200 miles trying to get the best mpg possible and ended up with 50. I get 45 when I ride normally. Maybe I'll check my valves soon.

When I changed to a 15t sprocket it made no difference to economy. Sometimes I even get better mileage than when I had the stock 16t.