why the crappy gas mileage?

I'm getting 46 with my 81 XJ 550. Carbs are running a bit rich. Should look into that...then I'd probably be doing better...who knows, maybe not?!?!

 

Second tank full after carb cleaning, much better then the first.
I got 35 mpg.
Was hoping for something closer to 45, but it seems in line with what others are getting.

 

Wel, my 2005 honda ruckus gets about 75-80 mpg on city commuting - I may be kicking myself in the butt, as I just transfered insurance to the '83 maxim 400 today. Another fellow I know in town with the same bike gets around 50-55 mpg, but he figures he should be able to get 60 if he fine-tunes the bike...

On the other hand, now I can go over 50 km/h, and stay the speed limit going uphill!!

 

I have been getting around 35 mpg on my XJ 650. Yesterday I did some mixture tuning using plug chops. I know my #4 was running very lean and 3 was somewhat lean. I don't have it perfect yet but on a ride yesterday I did notice I was now running 200 to 300 RPM less at 55, 65 and 75 mph. I assume that I got more power via the tune so hopefully this translates to more mpg.

I ordered a colortune to do the mixture settings right.

I also put half a can of seafoam in. I ran a few gallons at the normal concentration last week. That should help clear out any build up.

 

Partially correct. Ethyl alcohol (ethanol) is hydrophillic like brake fluid and readily mixes with water from 1% to 99%, including atmospheric moisture. The ethanol used in our fuels (for the last 10 yrs in my home state of MN) is anhydrous (without water) so it mixes readily with gasoline. Unfortunately, if it sits for a LONG time in a non-sealed fuel system (old cars and trucks before emissions systems, all small engines, and many motorcycles) it can absorb enough water to come out of solution with the gasoline. It doesn't "deposit" the water into your gas tank and stays fixed with the ethanol. Ethanol is flamable down to about 70% (140 proof) but it will come out of solution and wreck havoc on the air/fuel mixture. If you ride frequently, you'll never have an issue with ethanol. My bike gets over 45 mpg easily with Milwaukee's reformulated and oxygenated gasoline.

Now, as soon as the democrats get their fingers out of the free market cookie jar we'll be back to normal gas and more oil wells. Just because the poor oil companies have land leases doesn't mean there is oil there to be extracted.