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Discussion Starter · #1 ·
Hi, first time I’ve joined a forum and I’m on my third bike.

recently brought a 2002 zx6r 636 in red 61k (I know high mileage)

runs lovely when riding and when I come to a stop but quite quickly the idle speed become intermittent, drops very low then picks up and drops again every few
Seconds, the previous owner said the bike hasn’t been ridden more than 3 times in the last year. It has got worse over the last 2 weeks, it wasn’t doing it to begin with, and has developed then today it turned off. Will start up with a bit of throttle. The choke has also now stopped becoming effective, does not raise revs.

I have had a look at some threads and it sounds like I need to strip the carbs and clean the jets (I only know those terms from research, never done anything like that) I have seen other diagnoses like vacuum leak? I don’t know what that is.

would it cost a lot to get a local garage to do the carb clean?

thanks
Dan
 

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I don't know that you're at the point where you have a clear culprit. Many things can make the idle drop excessively when the bike is warmed up. Always best to start with a full tune up. Plugs, filters, oil, fresh fuel, and a valve clearance check. Once you have those items ticked, you can work your way into other potential issues. You don't know at this point if it's fuel, air, or spark causing the problem. Do the tune up, and reduce the variables so you can get to root cause in an efficient manner.

Many bikes use engine vacuum to determine a particular operational state..... this low pressure signal is most commonly sourced from the intake tract as the engine is sucking in air to run, which produces a low pressure zone in the intake. That pressure drop is consistent, and scales with RPM. More RPM, the greater the pressure drop (vacuum -- and it's really just a partial vacuum).

The rubber lines used to sample that vacuum are very small, and become brittle with age. As they lose elasticity and harden, they are more prone to cracking, which has the potential to change how strong the vacuum signal is.

If the lines on your bike have never been disturbed, there's a decent chance they still have a reasonable seal and provide the vacuum signature required...... then, the carburetors become a higher suspect, but I'd still want to know how the valves are doing with creating the actual vacuum in the first place. If they aren't opening as soon as they should, and closing too late, the vacuum signal will be weaker than expected. Same is true if they are opening late and closing early.
 

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Discussion Starter · #3 ·
Thank you, that all sounds a bit over my expertise. I took the air box off and filter was shot so put a new one in, sprayed carb cleaner in the carbs and seems slightly better but not sure if I’m being optimistic lol. It still cut out while it was warming up though the choke doesn’t raise the revs very much and cut out.
 

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I’m willing to bet it needs that tuneup, and then the carbs cleaned properly, and then synchronized.

The inside of the gas tank may be a mess…. Varnish or rust will cause lots of problems
 

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Discussion Starter · #6 ·
The local bike mechanics have quoted around £600 to do a full service, new spark plugs and do the valve clearances. Does that sound about right? Love the bike, would like to keep it for as long as it lives, what kind of mileage do these go to as mines already 61k
 

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If you want to save some money download the shop manual from here and tackle some of the easier tune up stuff. Oils/coolant changes and brake bleeding are fairly easy after watching a youtube vid or two.

If you want to save time on their labour charge remove as many of the fairings as you can before sending the bike to a shop. This helps speed up the time it takes and secondly you can store them safely at home.
 

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Thank you for the replies, will look into doing some of those bits myself, got a Haynes manual. Hopefully won’t be so much when it goes into the garage
Get the Kawasaki service manual from here:



Mark
 
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