Re: very bad gas mileage.
Mine wasn't quite that bad but it got lousy milage the first tank. Blubbering rich, rings not seated, low power so the throttle is open more all adds up.
I was also told to leave the jetting stock for a while but it ran so badly I changed the main and dropped the needle by the second tank.
Let your bike warm up for a couple minutes before you ride, it seems to help the milage quite a bit. When cold, it sucks some gas.
Now it will run in the mid 20s at half throttle and gets way over a hundred mpg riding easy.