Does the Electra have a 19" rear wheel? The 17 tooth sprocket is stock for the 19", the 18T is stock with the 18" wheel.
My G-5 averages around 72 mpg. You say you ride two up, that will definitely affect your mileage. My riding buddy weighs about 50 pounds more than I and he averages out in about the mid 60's. How hard you ride it can also make considerable. I don't ride very hard and short shift a lot, but manage to generally go fairly fast in the fun stuff. I out accelerate most traffic, but stop at the speed limit. At 62-65 on the freeway, my mileage drops to about 68 mpg.
I just use regular ethanol-containing gas as much as it sucks. It's the lowest octane on the pump, (76 or 78). Theoretically, pure gas should get better mileage. It's just a bother to chase down, and think it only comes in the higher octane modes.
Ah, just thought about it, you have a carb, they don't get as good of mileage as the EFI ones, but around 60 mpg should be in the cards. You have a lot more adjustments that can be off than are available on the later bikes.
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