Erratic Idle / Flat spots in RPMs / Poor MPG

[Zyphar]

Hey guys,

I have been having a problem ever since i bought this 01 Kat. The idle has been erratic whether it is hot or cold keeps jumping around. When the engine is cold, there are very apparent flat spots around 3k or so as well.

I figured it is the carburetors and a need for a valve adjustment but I cleaned out the carbs, did the valve adjustment, and changed the spark plugs with hardly any improvement.

I did not do a vacuum carb sync but I did do a visual carb sync (lining all the air ports to be about half way) and it did not improve. I am trying to locate one around the area, first thing to do next.

Here are the Symptoms

When cold: Starts fine with no choke but if choke is on, I need to blip the throttle abit to get it to start. MAJOR Flats spots on the RPMS ex. I take it slow but I feel little to hardly any power under 3k then but it suddenly kicks in at around 4.5k. Idle jumps around from 1.4k to 2k randomly. If the idle does stays at a spot below 2k, it hovers around it +-150 RPMs. If you rev it (slow or fast), the RPMs drop slow.

When hot: Idle jumps around still from 2.2k to 1.2k. If the idle does stays at a spot below 2k, it hovers around it +-150 RPMs. RPMs go down slowly (slow or fast) as well if you rev it. I notice that the idle increases if I put the bike on the side stand.

In either case, the idle adjustment doesn't help any because it might be fixed on one ride but not the other.

I am also getting poor gas mileage. I only about about 133 miles on a tank.

I haven't checked out the air filter yet nor to see if the plugs to see if it is sparking but the bike can move all the way to 10k no problem (no flat spots in the upper RPMs).
Oh and the Air/Fuel screw is set about 2 1/4 turns. I did notice that the diaphragm on the upper part of the carbs are abit out of shape, could this be a problem?
I also noticed that the lights dim below 2k or so, but i know that my battery is abit worn out. I realize it will dim some but just to be sure...Is it normal?

EDIT: I just rode at school and I realized that I was at half-throttle at about 1.5k with NO power. scared the crap outta me since there traffic behind catching up quick!
reason probably is because i filled the tank with 89 octane (10% ethanol so i figure it would be abit better) but I was wrong. It never did this with 87 octane.

[Anonymous]

check your floats sound like #1 #2 are set wrong speaciall the side stand thing fuel runs to the left more pressure on the lower carbs

[The CyberPoet]

I'm also thinking the throttle cable(s) may be set too tight. Bike upright, turn the steering all the way to the right (to right-stop), engine off, open and release the throttle. If you don't hear a distinctive click when you release the throttle, you found one of the issues.

Cheers,
=-= The CyberPoet

[Zyphar]

alright well i adjusted the throttle cables because it was a little tight. I changed the oil with 20w-50 Castrol GPS Synthetic blend and amazingly the low RPMs really feel more powerful and smoother.

And I noticed that the bike's idle no longer rises when I put it on the side stand. could have been the throttle cables but dunno... Maybe she has just been acting good since I have treated her good

I still the the erradic idle though. I talked to a mechanic and he suggested checking for vacuum leaks around the airbox which I will check later.

Any other things i should check out?

[The CyberPoet]

Eratic idle (idle bouncing +/- 100 RPM every second or three) can be a desperate need for a proper carb sync.

Eratic idle in much larger bounces every 1 to 5 seconds is usually an intermittent vacuum leak, like a smooth cut or crack in a vacuum nipple cap or vacuum line, where when the vacuum rises, it tugs hard enough to open the hole, and when it falls again, the rubber pops back into place. Also check the drain hose from the airbox for a proper seal at both ends (sealed to the airbox and sealed at the other end).

Cheers,
=-= The CyberPoet