What might cause a 10 mpg drop in my fuel mileage

[burkbuilds]

I know this is supposed to be for the GZ, but I'm in need of some advice on an issue with my Kawasaki Vulcan I'd like some input from you guys (and girls). I've put over 30,000 miles on my Vulcan 500 since I bought it in May of 09, and it has been a very trouble free bike for me. I changed my gears out to 17/40 not long after I purchased the bike and I've been getting 58-60 mpg consistently since then up until about a month ago. My mileage dropped off to about 55 mpg and now I'm down to 50 mpg. I thought it might just need to have the valves adjusted, so I did that today and got them all set to mid values (several were on the tight side of the spec and one was loose) and although I felt like the bike had a little more pep than it has had lately, I just drove down to Atlanta and checked my mileage when I got here and I'm dead on 50 mpg. Now I realize that a lot of guys riding the 500 get that or less, but I've been getting almost 60 for a long time and now it has really dropped off in a relatively short period of time. The only other thing I've noticed is that I've had to use the choke more lately. Until some time in January, I rarely if ever pulled it all the way out, usually the first detente was all it needed, but lately I've had to put it on full choke for about 30-45 seconds and then drop back to the first detente for the next minute or two. Otherwise, everything is running fine. No problems maintaining highway speeds and I really can't tell any performance difference at all other than my mileage drop. I just put new plugs in in January after I first noticed the fuel mileage drop, and that didn't seem to make any difference. I also replaced the air filter after I started noticing this drop in mileage and I change my oil every 3,000 miles and it's not due for another 1,000 miles and the oil level is fine.

Anybody got any ideas?

Thanks for any input.

Burkbuilds

[blaine]

The only thing I can think of is a good carb cleaning,as you stated that lately you had to use more choke.
:cool:

[alanmcorcoran]

I don't know about georgia, but gas is formulated differently out here in the winter and the summer. I also don't know what impact this would have on mileage, but I suspect it has some.

More significantly, when I was having trouble with my carburetor on the GZ my gas mileage dropped to about 40 mpg until I got it resolved. I'm sure you've seen the endless carb cleaning threads on here - in my case I took it to the dealer after I could not clear it up myself (with the seafoam, etc.) I actually had to take it in three times before they actually cured the problem. I'm not sure what they did, but it was over a year ago and, even though I sometimes go as long as two to three weeks in between GZ rides (have three bikes now and sometimes I'm out of town for two weeks at a crack) I have not had the problem come back and my mileage is back up around 60 mpg ish. I think I had clogged jets, but I really don't know what it was.

[jonathan180iq]

I'm in Georgia and it must be different gas for the season.
Several different gas mileage logs back it up. Consistently lower in winter than any other time of the year.

Even now, I can't break 18 MPG in the Liberty to save my life, and it normally rides at 19+

[mrlmd1]

You're running darkside on that bike, right? Has that had any impact on your gas mileage since you put the CT on?

[burkbuilds]

I did notice about a 2 mpg drop in my mileage after changing over to the car tire, thanks for asking, I had forgotten about that. The winter gas may be hurting my mileage some too and I think I'll add some carb cleaner this week and see if that makes any difference. Someone on another forum asked about my chain and although I keep it well maintained and it doesn't have any noticeable wear on it and the sprockets look like new except for missing the paint on the teeth, it does have over 30,000 miles on it, so maybe it could be adding some resistance just through friction of the old pins or something. Thanks for the ideas and advice guys.

[Water Warrior 2]

Another item that might contribute to lower mileage. Dressing for winter you may be bulking up and creating a larger body to cause air flow resistance. That and material that isn't as slippery in the wind. I would have to agree that winter gas is the major culprit as mentioned.

[burkbuilds]

I added some techron to the tank a few minutes ago so maybe by the end of the week I will know if that helped any.

[spicciani]

ya update us i'm curious

[burkbuilds]

Just got in from Atlanta tonight and checked my mileage. After just one 5 oz. treatment of fuel injector cleaner in the tank, I'm back up to 56 mpg, which included about 45 miles around town in traffic before I left, so, I think it was mainly a dirty carb that caused my loss of gas mileage. Hopefully I'll grab a couple of more miles on this tank of gas and be back to the 58-60 I've become used to getting. Thanks for everybody's input on this, it is nice to know I can ask for help here and so many are ready to respond, great group.