Backfiring and uneven idle

[roncg41677]

Well, I've been having some issues with my 01 GZ. I should preface this by saying the bike sat in a shed for 2 years before I got it. Once we ran some good gas and some stabilizer through it, it ran fine for about 250 miles. It has just over 4k miles.

Then a few weeks ago I left work and right away it started sputtering. The throttle would just intermittently disappear, then come back. After a couple of miles, this problem got much worse, and it started backfiring, then would eventually stall. I pulled over, and noticed someone had changed the petcock to "PRI". I have no idea how long it had been in that position, as I hadn't even looked at it for at least a month.

Switched the petcock, and the problem persisted. The strange thing was, when the bike was in neutral it idled and ran fine. As soon as I would shift it in 1st, it would start sputtering under throttle twisting, backfire horrendously and then just die. I ended up pushing it about a half mile home.

I had some friends over who know a lot about bikes and we checked all the fuel lines for obstructions, they were clear. Checked the spark plug, it looked okay. We took off the carb and took it apart the jets seemed okay for the most part, but I don't know much about carbs, and the guys with me are Harley guys, so they weren't sure about the number of jets, etc. We put it back together and the problem was still there. Right off the start, sputtering, backfiring, even with flames sometimes.

My dad thought the problem could be that some rust or junk had broken off the inside of the tank and was obstructing the petcock/fuel filter (I didn't realize at the time there wasn't one.). I took the gas tank off and cleaned it out with some diesel fuel and BB's. It doesn't sputter or die anymore, but every time I let off the throttle I get some small backfiring, every time. And when it idles it doesn't sound even (it never has). The best representation I can give is this: ba-ba-ba-ba-baba-ba-ba-ba-bababa-ba-ba-ba, etc ad infinitum.

I've got a new spark plug I'll put in today or tomorrow, and another friend wants to help me give the carbs a much better cleaning.

Sorry for the long post, but that is the total history of the bike as long as I've had it. Any ideas on what the problem is? I've got a small amount of knowledge about engines. I'm comfortable tackling many issues, and am actually enjoying taking the bike apart to learn more about it .