Low Fuel Economy - Running rich, not sure why

[ds1506]

Hello everybody,

So I bought myself a 1999 GZ250 a few weeks ago as my first bike. I got it for a steal since the previous owner left the prime valve open the night before I picked it up. After oil change and a new spark plug, I got the bike running again. While it seems to run fine, I'm getting absolutely terrible MPGs for this thing (I hit reserve about every 70 miles). Now since I've been working on it, I've been noticing that the bike is not very stock, so I've come to see if you guys could maybe point me in the right direction to maybe boost the economy of the bike.

As far as things that I've noticed are different goes: The bike has an aftermarket exhaust and the air box was taken out and replaced with a pod filter (which is kinda dirty, but still ok). I attempted to adjust the fuel mixture screw (the cap was already removed) and it seemed to be already screwed in all the way (that's supposed to lean out the mixture, right?). The bike is definitely running rich though, the plug is blackened. There's also a noticeable smell of gas when I'm sitting in traffic. I'm not entirely sure what my options are on how to get the bike to stop running so rich and I'm on a bit of a tight budget so I'm hoping it's not too big of an issue.

It also seems to be consuming oil, it smokes occasionally from the front, I'm thinking about where the exhaust meets the engine. I figure I can keep on top of the oil thing until I get the fuel issue resolved first.

I put a couple caps worth of seafoam in a couple days ago, but I'm not sure if that'll really fix my problem or not. The bike operates normally, runs fine, and gets me back and forth to school, but I'd like to do more than a weeks worth of commuting before I have to fill up again. Any help is greatly appreciated and I'd like to thank you guys for supplying the service manuals here, they've been very helpful so far.

Here's a couple pictures of the bike while I'm at it:


That's the condition I bought it in, and it's the same condition it's in now more or less (I moved the tail light and licence plate and got it running, that's about it).