My bike when stock got 49 mpg over a 5 tank test, did earshave and larger jets (went to 42/142) with 2 shims under the needles. I'm now 46-48 mpg but with a bit more zip. Plug color is a hair dark but not bad; more of a darker caramel color instead of a light tan.
For mileage comparison I'm 185 lbs and run a medium sized windscreen with large bags. Most riding on country roads at 55-58 mph. I actually get about 1 more mpg on 65 mph roads (probably because of no stops and few turns) but mileage drops to 45-46 mpg when I run interstate speeds. Fuel mileage results over the last 17,000 miles have stayed pretty consistent except the few times I've discovered very small vacuum leaks, then the mileage drops a hair until I find and fix the vacuum leak.
A friend with a VN750 found air leaks on both carb boots (no clamps) He added clamps and suddenly he's getting about 10 mpg better mileage. A very small vacuum leak (like on the vacuum line to the petcock) will cost you 1-2 mpg.
It's funny,,,, with a vacuum leak you'd figure that mileage wouldn't drop because the air speed through the carbs would drop pulling less fuel from the jets. But I've found that instead mileage drops when you have a vacuum leak.
I'm one of those numbers guys who likes to figure their mileage pretty often, sometimes over several tanks to get a true average. My bike usually hits reserve at about 135 miles and needs about 2.8 gallons when I've just hit reserve.
hope this helps.
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