Topic: 78 CB550K PD46C Carb Fuel level?????

[Jimbo4871]

Hey everyone.  My Carbs are running rich and I'm trying to find out why.  NOTE: I'm running a 1978 CB550k with a Big Bore kit to 601cc, so I'm trying to tune it just right. 

Is this fuel level height correct??? Too high.....or is it correct???

PLEASE ONLY REPLY IF you have experience with this.  PLEASE DO NOT MENTION CB750's or CB550's 1974-76 (Different Carbs). 
ONLY 1978 CB550K Keihin PD46C Carbs.  I don't need this forum going in 20 different directions.  Thanks. 

Here is my carb set up.

Main Jet: 100 (Stock was 90, went to 100 due to big bore)
Slow Jet: 42
Needle setting: 2nd from the top
Floats set to: 14.5mm
Air Screw set: 1.5 turns from the bottom.

K&N Air Pods
4 into 4 straight pipe exhaust, no muffler, no baffles.   

[Bankerdanny]

I have to say that based on your setup it's suprising that you are rich. The PD's were tuned lean to begin with and the free flowing exhaust, bigger bore and pods should require an even larger bump in jets than you gave it.

Are you bsaing your conclusion that it is rich on the plug condition? If so, are you doing plug chops across a varieaty of RPM levels to determine where it is rich?

[flybox1]

+1 Bankerdanny.
get a few sets of NGK D7EA plugs and do some chops at different throttle positions.
general riding plug deposits tell you/us nothing specific.
fuel level in your test looks good, btw.  (assuming all carbs read the same level, here)

[Jimbo4871]

Sorry I forgot to mention, YES all four Carbs are measuring the same fuel height. 

I ride generally low end 1/4-2/3 throttle.  I live in Boston so I don't get too much highway ridding (Top end) 

The timing on the bike has a DYNA electric ignition, and the timing is SPOT ON, for both 1-4, and 2-3. 

Also my compressions are all around 135 +/-5. 

But my Spark Plugs keep coming out black (Too Rich) 

BANKERDANNY...... I'm baffled also about this.  Like you said these carbs usually run too lean, and every other forum I've read regarding these carbs states they run too lean. 

Any other ideas??  Lower float level maybe??

[flybox1]

put in new plugs, lean out your mixture screw .5 turns, and ride in those throttle positions.  check deposits.
if little to no change, raise needle one position, and repeat test.


and the $10,000 quesiton....OEM JETS and NEEDLES? or keyster junk?   

[Jimbo4871]

I just put in new plugs this afternoon so I will try going down to 1/2 turn from bottom on the Air Screw and see what happens. 

All carb jets/needles/ports are from Kiehin direct or OEM. 

[Vinhead1957]

Measure your plug caps too they could be too resistive weakening the spark

[flybox1]

I just put in new plugs this afternoon so I will try going down to 1/2 turn from bottom on the Air Screw and see what happens.

Too much.  1 turn out is plenty.  It's a decrease by 1/3rd from current setup.  It's big enough to effect a change unless your 42 pilot is just too big...

[Bankerdanny]

OEM vs aftermarket jets/needles is an important question. You simply cannot trust that aftermarket jets are the size they say they are.