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Just bought a YZF600R, idle problem, clogged jet ?
#1
Greetings forum. I just acquired a 30,000 mile YZF600R in nice condition. When I test rode it, everything seemed fine. The day after I rode it home, I noticed that it doesn't idle very smoothly. It starts fine with the choke, but even after it's warmed up, the idle rhythmically bounces around between about 900 and 1500 rpm. I've tried playing with the idle adjustment screw to no avail. It runs great and the throttle response is perfect above ~3000 rpm.

The previous owner only put about 4000 miles on it in the last 3 years. He said he hadn't ridden it in a while, but claimed to have put stabil in the fuel tank.
While I was waiting for my account to be activated, I searched the forum. It sounds like one or more of the jets in one or more of the carbs is clogged ?
I put a bottle of Techron fuel cleaner in the tank today and let it idle for a while, but it doesn't seem to have helped. Is Seafoam the next logical step ? Should I put it inside of the tank like the Techron, or go into the airbox and spray it directly into the carbs ?

If that doesn't work, and i went to a pro motorcyle mechanic, do you think they could fix it inexpensively ? Do the carbs need to be completely disassembled and cleaned, even if the problem is only at idle ? Or could they just replace the jets used during idle speeds ?

Ideally, I'd do the work myself. But I don't have a lot of free time. I don't have a garage, so there is no convenient place to do the work. I'm more into riding than wrenching.

Any advice is appreciated.
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#2
I've had good results with Seafoam. Had the same hunting at idle, but after a day or so of running Seafoam, it all cleared up.
If you do have to pull the carbs to clean, the pilot jet is the one you need to unclog. It is a skinny jet with tiny holes that can usually be cleaned out with carb cleaner and compressed air.
There is plenty of info on here to guide you through the cleaning, which I recommend doing yourself when you get time, but I seriously think you can ride it clean.
Member: 100,000+ Mile Club (2003 YZF600RR)
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#3
Thanks for the response.

I put seafoam in the tank, and have ridden another 150 miles or so but the problem persists.

I found another thread that recommended Berryman's fuel system cleaner. The poster in the thread said it's stronger than seafoam.
So that's my next step. If that fails, I guess I will try to manually clean the carb jets. I found a good thread on here with detailed pics.
This forum is a great resource.
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#4
Eazy Rider Wrote:the idle rhythmically bounces around between about 900 and 1500 rpm.
Is it the idle itself or just the tacho readings? It might be an error indication. I don’t remember correctly but if a circuit is broken, the reading bounce between certain figures.
Igor Kalinin
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#5
Buy Haynes repair manual, remove and clean carbs, buy carb vacuum balancer, balance carbs and enjoy!


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#6
yes, after the seafoam runs, its probably really that one carb is a bit out of sync.
this requires a gage and a bit of patience to sync up all 4 carbs.

if after that it still hunts for an idle (or is unacceptable low) it will be either a clogged a/f mix at idle, or a valve gap closing up out of spec.

I chased a low (900rpm) idle for a year, it was the intake gaps closing up. I reshimmed the valves to spec and the issue went away. but at 30,000mi I would not expect a shim issue.
as long as it doesnt stall out on you all the time, let it hunt, until you can work on it yourself.

Because, No, a pro mechanic will be charging you a lot of money to pull, clean and resync the carbs, its like a 4-8hr job.
Driver Funny #3:  The guy who took a left turn in a right hand traffic circle.
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#7
Vacuum leak in intake?
Valve clearance isn't too bad to check, a few hour job. Adjusting is a bit more timely.
Checking carb synch isn't too crazy hard..
Maybe throw a new fuel filter on just for the heck of it? Check petcock screens too? Though throttle response being okay at higher RPMs make me think it is getting fuel, but at low RPM just not sucking enough fuel in for some reason.
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