Idle RPM

S

shadowelement

Well-known member
Hello Guys!

So after about 2 weeks of taking apart my 99 Katana and putting her back, we seem to have some improvement. Petcock no longer leaks, gas tanks is now properly adjusted, all the required rubber springs\washers are installed, new pilot jets in carb and cleaned all the spark plugs. I also redone fender as it was...out of style, to say the least (pics attached).

Now with all that said and done, I had issue with bike "choking" and lights flashing(barely noticeable, like when your flashlight battery is about to die), you suggested to adjust idle speed, which I did to about 1150-1200, now it seems to react appropriately. The only issue remaining is jumpy RPM, it jumps for about 20-40 rpms constantly, but once in a while(with no pattern) it jumps up to 50-80 rpms, for a sec or so. What could be causing this?

I thought that perhaps my bike was not warmed up, so I allowed it to stay at its Neutral for over 10 min, but there seems to be no change whatsoever...Maybe I am not warming bike properly? Perhaps I should leave choke at full for a min or so? Its just the second the bike is on, if choke is fully on it ravs to 4-5k rpm off the bet, so I always thought that its too much, and I lowered the choke, but it seems like there is no middle ground to it, it either stays at 4-5k, or pretty much goes to 1150-1200 no matter how carefully I try to use the choke switch...

Ideas?

here are pics(the left one is before, other 2 are for after) :
2zyvhp5.jpg

no7qfp.jpg
 
Did you synch the carbs after re-installing them? It makes a huge difference in the way they run.
 
A carb sync has nothing to do with jetting or mixture adjustment. Out of sync carbs can cause the symptoms you describe... but so can other things
 
A carb synch is when you hook them up to a vacuum gauge (manometer), compare the vacuum and adjust to get them running the same. If this hasn't been done in a while, it can lead to rough/stumbling idle, hanging idle and general poor running. If you've done all the other work on the carbs it's well worth the time to synch. It's easy to do, and you can build a manometer for under $10.
 
a carb sync is done with those three screws between the carbs(with springs and paint on them) never ever touch those without the vacume gauge connected. they open and close all the butterflies, but there is only 3. for 4 carbs. now think about that. each screw does 2 at a time. opens one while closing the other.
 
One method I use when I sync carbs that helps is I use the tip of a sewing needle and i adjust the butterfly so that the tip of the needle just drags underneath the butterfly and the inlet shaft. I can get them all pretty close.

You start with carbs 1 and 2 then 3,4. And then 2 and 3. They will all be within a hair of each other.
 
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