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 .

[Moedad]

Is your air filter clean?

[music man]

Also I am not sure if this has anything to do with it or not, but your bike does have a fuel filter of sorts, connected to the inside the tank part of the petcock. Did you happen to take it out and look at it by any chance. And I also would ask "is your air filter clean.


Later

[Easy Rider]

Originally Posted by 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.

Have you posted this problem here before? It sounds vaguely familiar.

Anyway..... before you go tearing the carb apart again and possibly making matters worse.....

Stabilizer is NOT a good cleaner. You may want to start out with fresh gas and some good cleaner.....like Original Gumout Carb Cleaner or Berryman's B12.

It may be unfortunate that you "cleaned" the tank without knowing that you NEEDED to. You may have damaged the inner lining, which will cause you trouble down the road. After all else is said and done, you need to install a paper or ceramic inline fuel filter.

I'm not clear on the present condition. Are you saying that the ONLY remaining problem is the backfire?......that it is running OK otherwise ?? The idle uneven-ness might just be an idle speed that is too low.

Either way, you need to check for leaks, intake or exhaust. Also the boot between the carb and the engine can crack with age. The air filter must be OEM, unless other mods have been made, and the air box must be tight, including the plug on the bottom of the drain tube, and, of course, no holes or tears in the filter or the airbox. Unlike most applications, the airbox is BEHIND the filter, flow wise.

Exhaust leaks (ahead of the muffler) can also cause a backfire.

Good luck! Keep us posted. Please put your location in your profile.

[roncg41677]

Originally Posted by Moedad

Is your air filter clean?

Yeah, the air filter is clean.

Easy Rider,
I haven't posted here before, but I have posted this on the Total Motorcycle forums, if you frequent there.

Sorry, I didn't use the stabilizer to clean the tank. The old owner put some stabilizer in the tank when I got the bike, thinking it would help after the bike had already been sitting. ...I know :roll: .

I used Berryman's B12 after the tank was clean and it was gassed back up. FWIW, I did see some brown "stuff" on the bottom of the tank. Just on the lowest parts of the tank, not elsewhere. You've got me all freaked out now. I hope I didn't mess up my tank. O_o I's assume there's no way to look and tell if I damaged the lining?

The bike seems to be running MUCH better now. The only problem is the backfiring (and the uneven idle). I haven't taken it to work yet, because I don't want it to die in the middle of nowhere. I'll at least change the spark plug and the oil before I chance it.


music man,
I did take the petcock out. I was confused because I thought the service manual I downloaded showed the tubes on the petcock as the "fuel filters". I did look at them and noticed there were no large holes. Is that how it works? The gas just kind of flows through the tube itself rather than into any larger holes? I will look into a fuel filter.

[Easy Rider]

Originally Posted by roncg41677

I used Berryman's B12 after the tank was clean and it was gassed back up. FWIW, I did see some brown "stuff" on the bottom of the tank. Just on the lowest parts of the tank, not elsewhere. You've got me all freaked out now. I hope I didn't mess up my tank. O_o I's assume there's no way to look and tell if I damaged the lining?

The bike seems to be running MUCH better now. The only problem is the backfiring (and the uneven idle). I haven't taken it to work yet, because I don't want it to die in the middle of nowhere. I'll at least change the spark plug and the oil before I chance it.

Probably no way to tell about the tank. Just watch the upper part that you can see with a flashlight for signs of rust.

You may just need to run more B12 through it to finish the cleaning BUT you really need to check for those air leaks I mentioned. Might be an easy fix.

[roncg41677]

About the idle...

Is this nothing to worry about? Playing with the idle adjuster could fix something like that?

[patrick_777]

Originally Posted by Easy Rider

Have you posted this problem here before? It sounds vaguely familiar.

He explained the problem in his introduction post the day before yesterday. It gave me some deja vu too.

[patrick_777]

Originally Posted by roncg41677

About the idle...

Is this nothing to worry about? Playing with the idle adjuster could fix something like that?

This might seem like a silly question, but are you letting it warm up completely and have the choke completely off? The idle adjustment screw will only alter the speed AT idle (hence the name). If you're still getting lugging and/or stalling when you open the throttle, you're having fuel or air flow issues (probably the latter).

Do what Easy said. Check all the vacuum hoses and tubes on the bike for tightness and cracks. Even a slightly loose vacuum hose will cause all sorts of real problems.

[roncg41677]

[quote=patrick_777]

Originally Posted by "Easy Rider":14p1p8ct

Have you posted this problem here before? It sounds vaguely familiar.

He explained the problem in his introduction post the day before yesterday. It gave me some deja vu too.[/quote:14p1p8ct]

Sorry . Yeah, that's me.

Originally Posted by patrick_777

This might seem like a silly question, but are you letting it warm up completely and have the choke completely off?

I'll have to pay closer attention. After putting the tank back on and riding it for ~5 minutes the other day it was doing it. And I know the choke was off. As far as checking vacuum hoses, can I just look at them, or do I need to try to blow through them or something?

Thanks for all the help !