2003 GZ250 Dies at Idle and Wont rev past Half

farmkid4 · 06-26-2019, 08:00 PM

Hi guys I'm new here so a little info about me before I describe my problem. I am a computer tech my trade however I worked for about 2 years as a part time mechanic and went to school for machining. Know a bit about 12v car wiring etc. Carbs are something I'm not great with though and that is where I think my trouble is.

About the bike 2003 GZ250 I bought from a friend who needed the space back.
He had planned on bobbing it chopped the rear and started collecting stuff but life happened and it had been sitting for a year or 2. He had cut up the exhaust and welded some straight piping onto them. In the process one exhaust bolt got broke off so I milled that out had it welded and re-tapped it.

The airbox is removed with just a cheap pod filter on the carb now.

The bike starts up but wont idle on its own you need to give it a little throttle to keep it running. However it you try to rev the bike up it loses power sputters and dies. I can get a video clip if that would be helpful. Basically Im trying to figure out what I should do the carb seems pretty clean but Im not sure if the jets need to be changed because of the pipe/air filter or something?

whew sorry if thats a lot but I thought some of it would be helpful. Thanks for any help/ideas!

blaine · 06-27-2019, 11:01 PM

Needs to be rejetted or ideally put the airbox back on.

farmkid4 · 06-28-2019, 09:29 AM

Quote:

Originally Posted by blaine

Needs to be rejetted or ideally put the airbox back on.

Thanks for the input I've been reading and thought the jets might need to be changed. I think I might have the airbox though. If I can get the original airbox on would I still need to change the jets do you think?

-Kevin

Vegas Street Rider · 06-28-2019, 07:12 PM

The GZ has to have a balance of air and fuel and when you eliminate the back pressure by taking the muffler off and removing the airbox, you upset that balance. If you are going to keep the bike as is, as Blaine stated, you will need to re-jet the carb or put the original equipment back on. Just putting the air box back on won't get you the right flow. You also need to put some kind of muffler with baffles back on as well. Then you still might have to tinker with the carb.

farmkid4 · 06-28-2019, 09:08 PM

Quote:

Originally Posted by Vegas Street Rider

The GZ has to have a balance of air and fuel and when you eliminate the back pressure by taking the muffler off and removing the airbox, you upset that balance. If you are going to keep the bike as is, as Blaine stated, you will need to re-jet the carb or put the original equipment back on. Just putting the air box back on won't get you the right flow. You also need to put some kind of muffler with baffles back on as well. Then you still might have to tinker with the carb.

Okay thanks for the input. The PO cut off the muffler and welded pipes on so I wont be able to put the original exhaust on easily but Ill look into some other options. Sounds like jets are going to need to be changed for sure tho

06-26-2019, 08:00 PM	#1
farmkid4 Junior Member Join Date: Jun 2019 Location: NY not C Posts: 3	2003 GZ250 Dies at Idle and Wont rev past Half Hi guys I'm new here so a little info about me before I describe my problem. I am a computer tech my trade however I worked for about 2 years as a part time mechanic and went to school for machining. Know a bit about 12v car wiring etc. Carbs are something I'm not great with though and that is where I think my trouble is. About the bike 2003 GZ250 I bought from a friend who needed the space back. He had planned on bobbing it chopped the rear and started collecting stuff but life happened and it had been sitting for a year or 2. He had cut up the exhaust and welded some straight piping onto them. In the process one exhaust bolt got broke off so I milled that out had it welded and re-tapped it. The airbox is removed with just a cheap pod filter on the carb now. The bike starts up but wont idle on its own you need to give it a little throttle to keep it running. However it you try to rev the bike up it loses power sputters and dies. I can get a video clip if that would be helpful. Basically Im trying to figure out what I should do the carb seems pretty clean but Im not sure if the jets need to be changed because of the pipe/air filter or something? whew sorry if thats a lot but I thought some of it would be helpful. Thanks for any help/ideas! Login or Register to Remove Ads
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06-27-2019, 11:01 PM	#2
blaine Senior Member Join Date: Feb 2010 Location: P.E.I. Canada Posts: 3,784	Needs to be rejetted or ideally put the airbox back on. __________________ If at first you do succeed, try not to look surprised.
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06-28-2019, 07:12 PM	#4
Vegas Street Rider Senior Member Join Date: May 2015 Location: Henderson, NV Posts: 1,089	The GZ has to have a balance of air and fuel and when you eliminate the back pressure by taking the muffler off and removing the airbox, you upset that balance. If you are going to keep the bike as is, as Blaine stated, you will need to re-jet the carb or put the original equipment back on. Just putting the air box back on won't get you the right flow. You also need to put some kind of muffler with baffles back on as well. Then you still might have to tinker with the carb.
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