Engine running unevenly, bike lurching

jdrider · 06-30-2011, 04:20 PM

Hello all, I'm new to this forum. Hoping I can get some help.

My 2002 gx250 was in storage in my garage for the winter. When I took it out of storage I drained the bad gas, checked the line and pet cock, and filled the tank. I also changed the oil and gave it a new battery as the other one was pretty old.

It starts ok but not great. I have to let it warm up for a long time and still have to leave the choke about 1/4 out for a while, maybe 10 minutes. It idles rough, kind of sputtering. When I'm in gear it will lurch forward and seems to run unevenly. I've messed with the throttle stop screw which was probably not the best idea since I didn't use a tach. I can't tell now if it's too fast or slow.

My first thought was "dirty carb". I figured the old gas was probably not great for the fuel system. I've read a couple other entries on this forum and now I'm not so sure. :??: I wanted to see what others thought before I go pay someone to clean the carb. Air filter? Spark plug? Something else?

Thanks!
Jen

alantf · 06-30-2011, 04:33 PM

First thing..........Try putting carb cleaner in the tank and see what difference it makes. The carb is always a problem with the GZ, so regular doses of carb cleaner may be required. Try double the recommended dose for the first couple of tanks.

Second thing....... Don't ever adjust the slow running knob unless the choke is off, & the engine is thoroughly hot. Then it should be set to 1200 to 1400 RPM. :2tup:

jdrider · 06-30-2011, 04:40 PM

I'll give the carb cleaner a shot and get a proper tachometer in addition to a new spark plug (why not). I imagine those things will help a lot.

Thanks!
Jen

geezer · 06-30-2011, 07:26 PM

id pull the carb off. i have never had luck just poirng in some cleaner and it fixing anyting. but i am a very unlucky guy sooo :roll: whatever, anyway removing the carb is as easy as it looks lol

alantf · 07-01-2011, 05:44 AM

I think that putting carb cleaner in the fuel is the FIRST step. If that doesn't work, then removing the carb is the SECOND step. Try the easiest way first. It worked for me. :2tup:

blaine · 07-01-2011, 08:18 AM

Quote:

Originally Posted by alantf

I think that putting carb cleaner in the fuel is the FIRST step. If that doesn't work, then removing the carb is the SECOND step. Try the easiest way first. It worked for me. :2tup:

:plus1:

bonehead · 07-01-2011, 08:25 AM

Quote:

Originally Posted by blaine

Quote:

Originally Posted by alantf

I think that putting carb cleaner in the fuel is the FIRST step. If that doesn't work, then removing the carb is the SECOND step. Try the easiest way first. It worked for me. :2tup:

:plus1:

geezer · 07-01-2011, 08:29 AM

sure but im not afraid to loosen a few bolts and dive in head first. just sayin

jdrider · 07-01-2011, 10:24 AM

Update - checked the spark plug and adjusted the slow running knob properly (with a meter, not with the choke out) and still having some lurching, though it was better last night. The spark plug looked like it was new, so the problem is definitely not there. I'm going to clean up the air filter and check hoses tonight, mostly just because it needs to be done. I think the problem is the carb. I have cleaned carbs before (in my honda 400) and I can do it again, but I'd rather not.

I'm going to use some carb cleaner and see if that helps. I should also check the slack in the chain but I doubt that's the problem. Looked fine when I changed the oil 2 weeks ago.

The lurching isn't that bad so hopefully a little cleaner will do the trick. Pulling the carb will be my last resort. My gz was my mom's last. I have no idea what kind of maintenance was done. I'm the mechanically inclined one.

I hope I don't spend my weekend clean a carburetor, but there are worse things.

Thanks for the help!
Jen

**jonathan180iq** · 07-01-2011, 10:26 AM

....thinking about this, before you do anything else, make sure that all of your vacuum hoses are attached and secure. A small air leak can lead to a big problem. Surging, bucking and uneven idle are good signs that they might be an issue. Even a small leak is a big deal.

You only have 3 or 4 hoses to worry about. So give them all a once over just to be sure.

06-30-2011, 04:20 PM	#1
jdrider Junior Member Join Date: Jun 2011 Location: Kansas Posts: 8	Engine running unevenly, bike lurching Hello all, I'm new to this forum. Hoping I can get some help. My 2002 gx250 was in storage in my garage for the winter. When I took it out of storage I drained the bad gas, checked the line and pet cock, and filled the tank. I also changed the oil and gave it a new battery as the other one was pretty old. It starts ok but not great. I have to let it warm up for a long time and still have to leave the choke about 1/4 out for a while, maybe 10 minutes. It idles rough, kind of sputtering. When I'm in gear it will lurch forward and seems to run unevenly. I've messed with the throttle stop screw which was probably not the best idea since I didn't use a tach. I can't tell now if it's too fast or slow. My first thought was "dirty carb". I figured the old gas was probably not great for the fuel system. I've read a couple other entries on this forum and now I'm not so sure. :??: I wanted to see what others thought before I go pay someone to clean the carb. Air filter? Spark plug? Something else? Thanks! Jen Login or Register to Remove Ads
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06-30-2011, 04:33 PM	#2
alantf Senior Member Join Date: Nov 2008 Location: Tenerife (Spain) Posts: 3,719	Re: Engine running unevenly, bike lurching First thing..........Try putting carb cleaner in the tank and see what difference it makes. The carb is always a problem with the GZ, so regular doses of carb cleaner may be required. Try double the recommended dose for the first couple of tanks. Second thing....... Don't ever adjust the slow running knob unless the choke is off, & the engine is thoroughly hot. Then it should be set to 1200 to 1400 RPM. :2tup: __________________ By birth an Englishman, by the grace of God a Yorkshireman.
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06-30-2011, 04:40 PM	#3
jdrider Junior Member Join Date: Jun 2011 Location: Kansas Posts: 8	Re: Engine running unevenly, bike lurching I'll give the carb cleaner a shot and get a proper tachometer in addition to a new spark plug (why not). I imagine those things will help a lot. Thanks! Jen Login or Register to Remove Ads
	0

06-30-2011, 07:26 PM	#4
geezer Senior Member Join Date: Mar 2011 Location: dahlonega GA Posts: 563	Re: Engine running unevenly, bike lurching id pull the carb off. i have never had luck just poirng in some cleaner and it fixing anyting. but i am a very unlucky guy sooo :roll: whatever, anyway removing the carb is as easy as it looks lol __________________ 99 gz 250 and a currently dismantled fzr 1000
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07-01-2011, 05:44 AM	#5
alantf Senior Member Join Date: Nov 2008 Location: Tenerife (Spain) Posts: 3,719	Re: Engine running unevenly, bike lurching I think that putting carb cleaner in the fuel is the FIRST step. If that doesn't work, then removing the carb is the SECOND step. Try the easiest way first. It worked for me. :2tup: __________________ By birth an Englishman, by the grace of God a Yorkshireman. Login or Register to Remove Ads
	0

07-01-2011, 08:29 AM	#8
geezer Senior Member Join Date: Mar 2011 Location: dahlonega GA Posts: 563	Re: Engine running unevenly, bike lurching sure but im not afraid to loosen a few bolts and dive in head first. just sayin __________________ 99 gz 250 and a currently dismantled fzr 1000
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07-01-2011, 10:24 AM	#9
jdrider Junior Member Join Date: Jun 2011 Location: Kansas Posts: 8	Re: Engine running unevenly, bike lurching Update - checked the spark plug and adjusted the slow running knob properly (with a meter, not with the choke out) and still having some lurching, though it was better last night. The spark plug looked like it was new, so the problem is definitely not there. I'm going to clean up the air filter and check hoses tonight, mostly just because it needs to be done. I think the problem is the carb. I have cleaned carbs before (in my honda 400) and I can do it again, but I'd rather not. I'm going to use some carb cleaner and see if that helps. I should also check the slack in the chain but I doubt that's the problem. Looked fine when I changed the oil 2 weeks ago. The lurching isn't that bad so hopefully a little cleaner will do the trick. Pulling the carb will be my last resort. My gz was my mom's last. I have no idea what kind of maintenance was done. I'm the mechanically inclined one. I hope I don't spend my weekend clean a carburetor, but there are worse things. Thanks for the help! Jen
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07-01-2011, 10:26 AM	#10
jonathan180iq Super Moderator Join Date: Jan 2007 Location: Dalton, GA Posts: 3,996	Re: Engine running unevenly, bike lurching ....thinking about this, before you do anything else, make sure that all of your vacuum hoses are attached and secure. A small air leak can lead to a big problem. Surging, bucking and uneven idle are good signs that they might be an issue. Even a small leak is a big deal. You only have 3 or 4 hoses to worry about. So give them all a once over just to be sure.
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