Fuel Economy (MPG) after rebuild

[j_fitz7]

I just rebuilt my 1980 GS1000G with 2x over (1mm) pistions and didn't touch the carbs during the rebuild.

The average fule economy i saw before was 43 MPG, now i get 34 MPG. Tank used to be ~175 to reserve, now ~150.

Info:

It runs better now and i may flog it harder due to that,

I also removed a vetter fairing during the rebuild and the bike is now naked.

The old pistons were really carboned up and i ran premium before the rebuild to keep from pinging, now i run the cheap stuff and it runs great.

The rebuild was complete about 1000 miles ago and fuel economy has been about constant since the rebuild.

The bike had 67+K on the clock b4 rebuild.

Any ideas?

[drhach]

It should improve as the engine breaks in. Keep tracking it. That being said, you took off the fairing so it's a bit of an apples and oranges comparison. I'm not saying you got better economy with the fairing. However, you changed two variables at once. Fuel economy shoul increase as the engine breaks in though.

[GearHead]

On a freshly rebuilt engine, the tollerances between all the parts of the rotating assy are alot tighter. So it takes a bit more power to turn the crank, rods pistons, ect. It takes about 2000 miles (give or take) to break in a new motor. Your fuel milage should go up as the motor wears in. All other things being the same as before the rebuild of course.
Gearhead

[Steve]

Yup, it's a combination of all the stuff you mentioned.
The engine is tighter.
You admit to flogging it. (By the way, done correctly, that is a GREAT way to break in an engine. 8-[)
You removed a somewhat aerodynamic (although heavy) device.

With 1000 miles on it after a rebuild, I would think it's about time to check the valves. While you are in there, double-check your cam timing to make sure you have the correct number of pins between the timing marks, and also verify the cams are correctly timed with the crank. It's easy to be off by one pin and the bike will still run reasonably well.

.