Topic: max oversize for emulsion tube holes cb550

[my name is nobody]

I'm experimenting drilling mine, and don't want to take too much material out. How far oversize
can I safely go? Mine are at .036 now, .001 over. Drives better and plugs are looking better, but
want to go bigger with holes to see if things get any better performance wise. CB 550 k0 all stock..
TIA guys

[HondaMan]

I'm experimenting drilling mine, and don't want to take too much material out. How far oversize
can I safely go? Mine are at .036 now, .001 over. Drives better and plugs are looking better, but
want to go bigger with holes to see if things get any better performance wise. CB 550 k0 all stock..
TIA guys

When you get past .039", there is no further improvement. Try to leave the lowest 4 holes (closest to the jet) a little smaller, or the top end will go extra-lean, making it fall flat above 7000 RPM. If you already drilled bigger, just solder them shut and start over, at the same vertical positions.

[my name is nobody]

Will strive to keep bottom holes smaller. I am looking for a little more lean at around 15-35% light throttle,
hoping this will be the magic formula to stop black carbon fouling plugs. Only going .001 made a difference,
but its tempting to go a lot more...

[scottly]

hoping this will be the magic formula to stop black carbon fouling plugs.

Before you go hog-wild drilling the emulsion tubes, have you verified the level of the fuel in the float bowls via the "clear tube method"??

[my name is nobody]

Before you go hog-wild drilling the emulsion tubes, have you verified the level of the fuel in the float bowls via the "clear tube method"??
[/quote]


I just re checked them and they look to be set closer to the bowl seam than they should be. Maybe on the verge of flooding. It makes sense that the bike acts like
it does. Sometimes it runs sweet, then ragged in random fashion. Drilling the tubes
out .001 from stock did have a somewhat of a good effect smoothing things in certain throttle ranges. I do know float levels are critical. What doesn't make sense tho is I religiously set float levels to 22mm, with the proper gauge, and using genuine Honda needle and seat inlet valves. Guess it's time to adjust floats to 23mm and check clear tube? Black plugs and irradic good/bad running cycles
are driving me bat#$%* crazy, mainly because I've had the carbs off more times than I can count and It's making me forget the mission I should be on.

[flybox1]

hoping this will be the magic formula to stop black carbon fouling plugs.

Before you go hog-wild drilling the emulsion tubes, have you verified the level of the fuel in the float bowls via the "clear tube method"??

What?!?!?    bigger emulsion tube holes to 'stop black carbon fouling plugs'?   
youre only going to add more fuel to the problem.

Before you go hog-wild drilling emulsion tubes....just dont. 
Get the bowl fuel levels perfect.
...and then idle plug chop to get IMS set.

[Bodi]

Increasing the emulsion tube hole diameters adds more air to the bubbly fuel/air mix feeding the main jet, and does make mixture a bit leaner.

[my name is nobody]

Increasing the emulsion tube hole diameters adds more air to the bubbly fuel/air mix feeding the main jet, and does make mixture a bit leaner.

This was my thought as well. I do plan to reset float level a bit higher numerically, also, as I said before,  I clear tubed a bit too close to the bowl seam

[Deltarider]

I'm no expert and I admire your willingness to experiment, but I wonder what there is to win, if the mixture as it is now, is within the A/F range for a correct combustion. Do you have problems like misses that you seek to cure? I mean, what can be gained? Again, I'm no expert and read this thread with interest.

[my name is nobody]

been chasing a rich condition along with a 1/4 throttle random surge. drilled the emulsion tubes .001
larger to mix more air in with the fuel charge. It creates a leaner
charge, and I want to see how I affects drivability.  I'm getting closer. So far I have noticed
smoother cruising speeds, but believe floats are  still adjusted a little high also contributing to the richness
and black plugs. Float height is probably the most influential adjustment of all.
I'm going to concentrate on that before drilling any larger/more holes in the tubes. If I drill any more
holes it will be according to Hondaman's guidelines.

[HondaMan]

been chasing a rich condition along with a 1/4 throttle random surge. drilled the emulsion tubes .001
larger to mix more air in with the fuel charge. It creates a leaner
charge, and I want to see how I affects drivability.  I'm getting closer. So far I have noticed
smoother cruising speeds, but believe floats are  still adjusted a little high also contributing to the richness
and black plugs. Float height is probably the most influential adjustment of all.
I'm going to concentrate on that before drilling any larger/more holes in the tubes. If I drill any more
holes it will be according to Hondaman's guidelines.

By chance, are you running "pod" air filters instead of the airbox, filter, and plenum? If so, that's where the trouble is originating, and you will not be able to solve it by tinkering with the jetting. The pods fully destroy the mid-pressure air needed at the bell area of the carbs, making it impossible to let the emulsifiers do their job - they simply don't have any air pressure.

[my name is nobody]

been chasing a rich condition along with a 1/4 throttle random surge. drilled the emulsion tubes .001
larger to mix more air in with the fuel charge. It creates a leaner
charge, and I want to see how I affects drivability.  I'm getting closer. So far I have noticed
smoother cruising speeds, but believe floats are  still adjusted a little high also contributing to the richness
and black plugs. Float height is probably the most influential adjustment of all.
I'm going to concentrate on that before drilling any larger/more holes in the tubes. If I drill any more
holes it will be according to Hondaman's guidelines.

By chance, are you running "pod" air filters instead of the airbox, filter, and plenum? If so, that's where the trouble is originating, and you will not be able to solve it by tinkering with the jetting. The pods fully destroy the mid-pressure air needed at the bell area of the carbs, making it impossible to let the emulsifiers do their job - they simply don't have any air pressure.

All stock sir. Just finished up putting it back together a few mins ago. Only parts I am missing are
plenum drain hose and airbox drain hose for pcv system.  even air cleaner is genuine Honda. 100 mains/38 slows, needles at 2nd groove from bottom.

[calj737]

...needles at 2nd groove from bottom.

That is awfully rich for a stock bike setup 

[my name is nobody]

supposedly correct in that groove. I have about a dozen 022a parts carbs and they are that position too.
I'm going to watch the plugs for a while, and see if 1 cylinder is burning different than the others. I have
checked/tried/adjusted everything I can think of recently and suspect there's only 1 carb screwing up
(for whatever reason) causing problems. This being the case after I tweaked float levels to 23mm.
from 22mm. clear tubes close now and plugs are new. but still has classic feel of a rich cruise condition when maintaing 10-20% throttle. gets better when accelerated. I can't find anything after that, plug chops will be next if there is a place where I won't get killed in traffic doing it. Time to take a break from it
I will report a fix if I find one, and thanks to all to this point.

[RAFster122s]

Bringing your needles up one notch is going to lean out your mix and then you adjust to fatten up the mid range and upper end.  Tuning so your normal cruise/riding speed and idle are spot on will go a long way towards better operation...10-30 % range of your throttle is being used a lot?  I keep the revs up so it is closer to the power band...10-30% you must be in very slow traffic and creeping along.
4k is a pretty good start but 6k and above are where a 550 is happiest.  Granted we will rarely have wot roads and spaces...

[HondaMan]

been chasing a rich condition along with a 1/4 throttle random surge. drilled the emulsion tubes .001
larger to mix more air in with the fuel charge. It creates a leaner
charge, and I want to see how I affects drivability.  I'm getting closer. So far I have noticed
smoother cruising speeds, but believe floats are  still adjusted a little high also contributing to the richness
and black plugs. Float height is probably the most influential adjustment of all.
I'm going to concentrate on that before drilling any larger/more holes in the tubes. If I drill any more
holes it will be according to Hondaman's guidelines.

By chance, are you running "pod" air filters instead of the airbox, filter, and plenum? If so, that's where the trouble is originating, and you will not be able to solve it by tinkering with the jetting. The pods fully destroy the mid-pressure air needed at the bell area of the carbs, making it impossible to let the emulsifiers do their job - they simply don't have any air pressure.

All stock sir. Just finished up putting it back together a few mins ago. Only parts I am missing are
plenum drain hose and airbox drain hose for pcv system.  even air cleaner is genuine Honda. 100 mains/38 slows, needles at 2nd groove from bottom.

Depending on which 500 this is (1971 or 1972 model), the needles might be in the center notch, too. This will lean it out 1% from where it is now. My brother had the first-year 500 and the needles were in the 4th notch with #98 mainjets, mine was the next model and they were middle notch with #100 mainjets.

[my name is nobody]

As mentioned earlier, I modified the emulsifier tube holes to .036 (cb550k0) to try to get rid of carbon fouled
plugs. with drivability issues at light throttle cruise. Since that first tube modification, I went back and lowered float levels to 23mm. float setting, and changed plugs. Problem persisted, but plugs looked cleaner.
(put a hundred miles or so, mixed driving). Plugs were normal for 1 3 4, but cyl #2 still black carbon fouled.
These carbs have been rebuilt with genuine Honda, and were not flooding. I had a spare #2 carb body,
that was a different number than my other 3 (022a), and I decided to exchange guts from the 022a to the other mismatched "non" 022a carb. The carb number escapes me, but it all fits. Viola, the drivability problem
is gone and the plug for that cylinder looks good at this time. Something is up with o.e. #2 carb body.
A stopped up air or fuel passage somewhere. Hopefully no adverse affects from miss matched carb numbers
and calibrations. Seems to run fine after vacuum sync and test drive. I'm a happy boy once again.