Inconsistent Idle

Narsil · 05-31-2024, 09:40 AM

Hey all! I recently got a 2000 GZ250 Marauder for the Wife to learn on. Had to put a new stator and battery in it. Cleaned the carb (completely stripped 90' soapy water for a few hours, compressed air through all passages including pin-holes, followed by acetone and more compressed air). Repaired a hold in the exhaust, extracted a broken exhaust manifold bolt and replaced them all with stainless bolts.

She's loving it, it's a great bike! But it doesn't idle well. You can set the idle, and it will sit there, and then it will slowly start to die, so you turn up the idle, up and up, and eventually it stabilizes and will seem to be idling well, so you go for a ride, but after running at higher rpm for a while, you come to a stop, and now the idle is way to high. So you lower the idle, down down down, and it idles well, but then if you let it sit for a bit like that, it'll slowly degrade and die. So you idle up up up, and start all over again.

I'm thinking there is a leak somewhere that fluctuates with temperature. I've tried spraying carb cleaner around the carb boots, and couldn't see any sign of it getting sucked in. I tried blowing propane from my torch around the boots as well, and could hear no change in the engine. I'm thinking of taking the top end apart, cleaning valves, replacing seals, maybe rings.

But I'm looking for ideas or suggestions, any ideas? Let me know!

Wijohn · 06-20-2024, 01:38 PM

I missed this post, I have had some of those problems. When you cleaned the carb. did you check the jets? The pilots jet could be your problem. Or the other problem which I think is more likely be that you could be running too rich
Easy method to tell is rev the engine, release throttle, if correct it should quickly drop back to your idle speed. I am no expert but I try.

Vegas Street Rider · 06-20-2024, 03:24 PM

I had that issue and in my case it was the diaphragm in the petcock. I put a kit in it and that resolved it.

I am also a big proponent of running Seafoam in my fuel about every three or four tank-fulls. It keeps the jets clean.

Axeman88 · 06-20-2024, 04:36 PM

I'm getting the drifting idle on my '06. Gets faster as the bike gets hotter, and seems to hang at high rpms. In the past, I've associated this behavior with a vacuum leak, possibly through the carburetor mount boot.

But, I also figure that when a manufacturer puts a KNOB on the idle adjusting screw, which is easily accessible from the saddle, such as is on my GZ250, they may be telling riders that they KNOW from the Get-go that idle is going to drift, and are giving you a work-around.

Because, a lot of machines do NOT have a knob on the idle adjustment and bury the adjuster somewhere very inaccessible.

05-31-2024, 09:40 AM	#1
Narsil Junior Member Join Date: May 2024 Location: Peterborough, ON Posts: 3	Inconsistent Idle Hey all! I recently got a 2000 GZ250 Marauder for the Wife to learn on. Had to put a new stator and battery in it. Cleaned the carb (completely stripped 90' soapy water for a few hours, compressed air through all passages including pin-holes, followed by acetone and more compressed air). Repaired a hold in the exhaust, extracted a broken exhaust manifold bolt and replaced them all with stainless bolts. She's loving it, it's a great bike! But it doesn't idle well. You can set the idle, and it will sit there, and then it will slowly start to die, so you turn up the idle, up and up, and eventually it stabilizes and will seem to be idling well, so you go for a ride, but after running at higher rpm for a while, you come to a stop, and now the idle is way to high. So you lower the idle, down down down, and it idles well, but then if you let it sit for a bit like that, it'll slowly degrade and die. So you idle up up up, and start all over again. I'm thinking there is a leak somewhere that fluctuates with temperature. I've tried spraying carb cleaner around the carb boots, and couldn't see any sign of it getting sucked in. I tried blowing propane from my torch around the boots as well, and could hear no change in the engine. I'm thinking of taking the top end apart, cleaning valves, replacing seals, maybe rings. But I'm looking for ideas or suggestions, any ideas? Let me know! Login or Register to Remove Ads
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06-20-2024, 03:24 PM	#3
Vegas Street Rider Senior Member Join Date: May 2015 Location: Henderson, NV Posts: 1,105	I had that issue and in my case it was the diaphragm in the petcock. I put a kit in it and that resolved it. I am also a big proponent of running Seafoam in my fuel about every three or four tank-fulls. It keeps the jets clean. Login or Register to Remove Ads
	0

06-20-2024, 01:38 PM	#2
Wijohn Junior Member Join Date: Apr 2024 Posts: 12	I missed this post, I have had some of those problems. When you cleaned the carb. did you check the jets? The pilots jet could be your problem. Or the other problem which I think is more likely be that you could be running too rich Easy method to tell is rev the engine, release throttle, if correct it should quickly drop back to your idle speed. I am no expert but I try.
	0

06-20-2024, 04:36 PM	#4
Axeman88 Junior Member Join Date: Jun 2024 Posts: 22	I'm getting the drifting idle on my '06. Gets faster as the bike gets hotter, and seems to hang at high rpms. In the past, I've associated this behavior with a vacuum leak, possibly through the carburetor mount boot. But, I also figure that when a manufacturer puts a KNOB on the idle adjusting screw, which is easily accessible from the saddle, such as is on my GZ250, they may be telling riders that they KNOW from the Get-go that idle is going to drift, and are giving you a work-around. Because, a lot of machines do NOT have a knob on the idle adjustment and bury the adjuster somewhere very inaccessible.
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