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Discussion Starter #1
Just purchased a 1990 600r. It runs real great except that it takes a second or two to return to idle when reved up or when shifing gears. It also sounds like it has a slight miss when at a constant speed. Does not miss at acceleration or deceleration.

It has a 4 into 1 header, vance & hines pipe, and a K & N air filter. The rest is stock.

I cleaned the carbs (they were real bad). That seemed to help. But I know there is something else off. Thanks
 

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I can think of two thing for starters that will cause a bad idle, carb sync and valve adjustment. I would start by syncronizing the carburators.
 

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swjohnsey gave you a good starting point.
Jetting may also be a concern.

Diirk
'99 ZX6R
'02 Raptor
'01 Wolverine
'87 Radian
 

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Did you replace the idle/slow speed jets at the same time as the main jets? They tend to be over looked quite often.

Also, since you have it apart, you might need to adjust the idle speed mixture screw. since you added both pods and an exhaust system, you leaned out the mixture, so you will have to richen up the idle circuits to match.

Another 1/4-1/2 turn either in or out per carb should set the idle straight.

Also, you might want to replace the needles just by the age of the bike. Since you went through the trouble of changing the mains, it only pays to replace the needles at the same time.

BC.
 

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Discussion Starter #7
I did not replace the idle jets, I only replaced the main jets because I had some laying around.

I had already richened up the idle screws 1/4 turn. It does NOT have pod filters, just a K&N replacement. I would like to change to pods but how do you get around the large vaccuum line into the airbox??

I oiled the throttle cables and that helped the return better.

Would the missing be from the needles set too lean?
 

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Try following the cleaning up with 2 shotglasses filled with chevron Techron Fuel System Cleaner. Add the two shotglasses to a full tank of gas, and ride the tank until you hit reserve, then fill up again with another pair of shotglasses full of the cleaner.

You might not have gotten every last bit of gunk out of the carbs.

Also, to get around vacumn lines, you could run a t-fitting, and make a couple holes in the pods, and feed the vacumn line through ports in the pods. Just make sure that you use silicon sealer when you install fittings into the pods.

BC.
 

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Discussion Starter #9
Thankx for the ideas. It will be nice to get that damn airbox out of there. It took me almost an hour to get the carbs out because of that box.
 
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