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Hello all, I recently picked up a 1992 FZR600. It ran when I got it but the idle has always been all over the place. I was able to get it somewhat stable at 1500 rpm by using the choke but I want to fix the problem for good. No matter how I try to adjust the idle with the adjuster screw it will either idle at about 3k or chug along at 1k for a few seconds but then die. However, it will rev up fine in neutral and quick rides through my neighborhood seem normal.

The first thing I did was put in new NGK plugs and clean the carbs. I took the carbs apart and sprayed carb cleaner through each passage. Still had the problem so I tried my hand with valve lapping a spare head that came with the bike and swapped it to the bike. No luck. I couldn’t get it to idle well enough to get the carbs synced either, but I did bench sync them with a sewing needle to get close.

At the battery I get about 12.8v at 3k rpm which according to the manual is a little low, but it does have the R6 R/R swap so I’m not sure if that changes the running voltage at all.
Any advice on what might be wrong or what to try next would be greatly appreciated!
 

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Have you checked for vacuum leaks? Especially around the carb boots?
 

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Discussion Starter #4
I did try to find vacuum leaks by spraying carb cleaner around the carb boots. I didn’t find any leaks when I did that. Are there any other places I might be getting a leak?
 

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You can check for leaks where the carbs connect to the air box but this usually doesn't affect idle. I am dealing with this same issue on a Ninja.
 

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It does the same thing whether the air box is on or not. I bench synced the carbs but maybe they need to be actually synced?
What about the emulsion tubes? I read that they can get worn out and cause problems.
 

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I wonder if the emulsion tubes could be plugged?
 

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I think I figured it out. Sharkmonkey was right about it being the emulsion tubes. I was able to get another set of carbs from a friend and when I compared the emulsion tubes to mine, I noticed that mine were larger down the bore even though they were both the same size (Y-0). So that caused my bike to run super rich (no choke needed, hanging idle). Now I just need to go get them synced. Thanks everyone for all the suggestions.
 

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Hello all, I recently picked up a 1992 FZR600. It ran when I got it but the idle has always been all over the place. I was able to get it somewhat stable at 1500 rpm by using the choke but I want to fix the problem for good. No matter how I try to adjust the idle with the adjuster screw it will either idle at about 3k or chug along at 1k for a few seconds but then die. However, it will rev up fine in neutral and quick rides through my neighborhood seem normal.

The first thing I did was put in new NGK plugs and clean the carbs. I took the carbs apart and sprayed carb cleaner through each passage. Still had the problem so I tried my hand with valve lapping a spare head that came with the bike and swapped it to the bike. No luck. I couldn’t get it to idle well enough to get the carbs synced either, but I did bench sync them with a sewing needle to get close.

At the battery I get about 12.8v at 3k rpm which according to the manual is a little low, but it does have the R6 R/R swap so I’m not sure if that changes the running voltage at all.
Any advice on what might be wrong or what to try next would be greatly appreciated!
I hate when I need to broing someone back with his/her/it's legs to the ground... (LOL) This bike is almost thirty years old. How many miles are on the dash? If a lot, I'd do a compression test. You talk about cleaning the carbs with carb cleaner... Did you jet them? So many things could be at fault... Start by doing a compression test if it's high mileage.
 
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