Idle Mixture Screw Factory Setting - - The home of the Kawasaki EX500 / Ninja 500R
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post #1 of 5 (permalink) Old 8-29-2011, 2:52 PM Thread Starter
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Idle Mixture Screw Factory Setting

Hello all!

Been a member of the forum for a while but havent posted anything yet. My wife's 09' Ninja 500 has 900 miles on it, and developed an odd idle issue all the sudden after starting it yesterday. It developed a slower idle and smelled rich, and the choke did not have the same effect on the engine as before. Long story short, checked the plugs(loose), put fresh gas in it, Went ahead and ran the valves(3 exhaust valves were a "tight" .007", fixed that) to no avail. Reluctantly I removed the carburetors and disassembled them and cleaned them thoroughly. Believe it or not, problem ended up being brass machining bits residing in one of the SEALED(!) mixture screw wells between the o-ring and the end of the needle!! Must have been in there all the while and decided to give me problems just recently, the needles looked just fine.

Anyway, question is- One of the mixture screws was 1.5 turns off the seat and the other was only .75 turns off the seat. Oddly, the bike runs perfectly. I do recall that one plug looked slightly leaner than the other. This is this bike's paticular factory setting, so I put them back EXACTLY where they were. Should I go ahead and turn the lean screw out to 1.5 to match the other, or leave it since it runs good? Thanks in advance!!
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post #2 of 5 (permalink) Old 8-29-2011, 2:59 PM
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Re: Idle Mixture Screw Factory Setting

If you dove that deep into it, I'd take it a step further and drill the airbox (1 - 1" hole or 4 - 1/2" holes or equivalent), optionally throw in a K&N air filter (to complete the FOG mod), and turn the screws to 2.5 turns each. Then adjust both of them in the same direction in or out by the same amount to find when the bike runs best. Then sync the carbs with a store-bough or a man-made manometer.

[quote author=FOG link=topic=34059.msg506644#msg506644 date=1315092156]<br />"The only part of the carb I couldn't get to are the jets inside the deep hole."<br /><br />The only part of the carb that needs cleaning are the jets down in the deep hole.<br /><br />FOG<br />[/quote]<br /><br />EPIC FOG!
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post #3 of 5 (permalink) Old 8-29-2011, 10:16 PM
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Re: Idle Mixture Screw Factory Setting

its running too lean if the plugs show it. set them to 2-2.5 turns out do the air box mod, synchronize the carbs and it will start better when cold(almost instantly choke fully on) and run better at slower speeds(less lugging).

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post #4 of 5 (permalink) Old 10-1-2011, 1:36 AM
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Re: Idle Mixture Screw Factory Setting

The idle needles on my XJ650 were factory set at: 3 7/8, 3 3/8, 1 3/8 and 2 3/8 turns - all over the place. One wonders how four identically engineered cylinders and carburetors can run well with such an idle mixture variation. Supposedly, they were set with a sniffer in each pipe at the factory, since each head pipe has a smog bung in it. Problem is that they can only set the smog on a zero-mile engine when they do this. They have only to show that it met smog regs when it went out the door. Apparently, they expected the dealer to clean it up if the customer complained about it. However, the EX has no smog bungs in the head pipes, so I really wonder what their reasoning was.

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post #5 of 5 (permalink) Old 10-1-2011, 7:25 AM
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Re: Idle Mixture Screw Factory Setting

The factory carb settings were made at the Kehin factory quite removed from the Kawasaka engine. and were done on a flow machine. The variance is only a reflection of the rate of flow of each carb (set to K's requirments). Normally you may set them the same once installed on a running engine. Now your adjusting for all the variations of the engine as well as the carbs, for best performance. This was never Ks Idea, only to emit the desired amount of emmissions.


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