Topic: CB550: Flat spot better but still poor mileage. STILL RICH :( See page 4

[Scott S]

 Duano and Matt....
 Yes, I cleaned the slides and needles with 0000 steel wool. Everything moves freely and fits where it should.

 All cylinders are rich.

 A few Q's:
 - Where can I get a jet gauge? While I've verified that these are genuine Keihin jets and are marked 100, who knows what evil Previous Owners do? It's possible that someone has drilled these jets out.

 - Where can I get the O-rings that fit on the push in main jets? These have been replaced, but I'd like fresh O-rings if I use the jets from the 627B carbs. Don't they have to be nitrile or something? What size are the O -rings?

 - Is there such a thing as smaller push-in mains? I have 100's (supposedly). I can only find 98's which, to me, wouldn't make much of a difference.

 
 To recap: The carbs have been cleaned multiple times. Emulsion tubes, needles, slides, jets, passages, etc. are all good and marked with stock numbers. Floats are set correctly. Needle has been dropped one notch. Timing is advanced slightly. Stock 550 motor with Uni-Filter in stock air box and a MAC 4-1. Pamco ignition with new coils from Z1, new caps, and plugs have been swapped out and/or cleaned several times.
 I had the stock CB500 engine in this bike with all the same ancillaries. It ran fine and returned high 30's to low 40's MPG. I did nothing but swap in the 550 engine and carbs. Same exhaust, same coils, same air box, etc., etc. It runs extremely rich and gets very poor mileage.

[Scott S]

 Checked the caps, coils and kill switch today. Everything Ohm'd out OK. Pulling out my hair here....

 Gonna try the performance baffle, I guess. I also ordered some o-rings today. I guess I'll try some other main jets in the off chance that someone drilled these out. I have some used Keihin mains and some new aftermarket mains from a rebuild kit. The aftermarket ones aren't marked, but I'm guessing that they're supposed to be 100's, since they came from a stock rebuild kit.

 Still hoping for some fresh insight/suggestions.

[dawdish]

Wow, I've been following this thread for a while now. thought you had it figured a while back. I have this same set up, hence my interest. CB 500, 550 carbs, pods, exhaust....I'm running 100's, and they're on the edge of rich for my altitude, 6000'. I changed out the coils this summer, to Dynas', and it made a big difference, especially @ 8000-10000' . Dime City has good jets, thats where I got mine, and they're marked, and come w/orings.

[matt mattison]

I was having the same issue with one cylinder only. Went through all the same steps and that one cylinder never would clear up. Finally, and I mean finally, I pulled the needles and emulsion tubes to check the fit of the needle in the emulsion tube. What I found was the offending cylinders emulsion tube seemed worn. With all four sets apart on the bench I checked each one by fitting them together. The worn one was obvious,and I had local motorcycle mechanic look at it too to confirm myself. The needles all were fine. I verified that with my micrometer. A new set of honda needle and needle jet (emulsion tube) cost about $30 a set (each carb). If your at wits end maybe just check it out. Buy one set and see if that clears up that one cylinder. If it does, go for the other 3?

[Scott S]

 Matt: How did you determine it was worn?

[Scott S]

 Dug into a set of 627B carbs that I pulled out of the junkyard a few years ago. Pulled the slides, needles, jets and mixture screws. Everything is soaking in a bucket of Berrymans right now.

 I was sort of expecting to see differnt numbers on the slides and needles (different that what's in the 087A carbs), but they're all the same.

 Slides   : 103 2.5
 Needles: 272304
 Clip pos: 4th groove from top
 
 The mains are unmarked. The pilot jets in the carbs were 40's, compared to 38's in the 087A's.
 When the O-rings arrive, I'll pull the carbs AGAIN and quadruple check that the main air jet (tube that feeds the emulsion tube) is clear, but I know I've cleaned it. I'll try some different mains, too.
 Can anyone tell me how to check for wear on the emulsion tubes and needles? 

[lucky]

The needle valves and seats were cleaned and lapped in and then tested with a vacuum. Still....who knows?

 My plan is to check the o-rings, try adjusting the air screws a little again and pulling one of the float bowls to confirm jet sizes.

 I just want to make sure that I'm going the right way if I lower raise the needle/smaller main if my issues are as described above.
 My initial thought was to LOWER the needle and/or a smaller slow jet.

 Hondaman, where are you !?!?

I was reading through all of this thread and when I saw "The needle valves and seats were cleaned and lapped in and then tested with a vacuum. Still....who knows?"

You cannot polish your way into having good parts.
I would replace the needles and seats if they are both metal.
Also if the needle is the rubber tip style just replace all of the needles and set the float levels the way the workshop manual tells you.

It is hard to read through all of this text and pick out the important facts.
You do not need a jet gauge. You can use a precision steel ruler or vernier calipers for measuring the float levels.
BTW...DAWDISH is at 8,000-10,000 feet altitude. (disregard this info if you are not at  that extreme altitude.)

I will try to unsnarl this mess.
Facts:

CB550 engine.
Mac 4 into 1 exhaust.
Intake, Unifilter in stock air box.
Needles dropped one notch??? from where?
We need to know counting from the top,which notch the clip is set on the needle.
ENGINE timing not correct. Needs to be set to stock specs.
Stock needle setting 4th from the top.
Mainjet #100 stock , I would use 105 mains to start with that 4 into 1 exhaust just to make sure it is not lean at WOT.
Idle jet with 4 into 1... #38.
Needle setting stock 1.5 turns.
If you install the "performance baffle then you will have to START ALL OVER>
Carbs are LAST.

[Scott S]

I will try to unsnarl this mess.
Facts:

CB550 engine.
Mac 4 into 1 exhaust.
Intake, Unifilter in stock air box.
Needles dropped one notch??? from where?
We need to know counting from the top,which notch the clip is set on the needle.
ENGINE timing not correct. Needs to be set to stock specs.
Stock needle setting 4th from the top.
Mainjet #100 stock , I would use 105 mains to start with that 4 into 1 exhaust just to make sure it is not lean at WOT.
Idle jet with 4 into 1... #38.
Needle setting stock 1.5 turns.


 

From page 2: "The clip IS on the 4th notch from the top." I lowered the needles by moving the clip up one notch. This SHOULD have leaned me out.
 Also from this thread:
 I already have 38 idle jets.
 The mains are marked 100 and genuine Keihin.
 Timing was slightly advanced in an attempt to help mileage.
 All of this information is contained in this thread. I don't understand why it's rich. I think I have some needle/seats from a rebuild kit...the metal tipped ones. I'm willing to try that when the carbs are off again.

[Scott S]

Mainjet #100 stock , I would use 105 mains to start with that 4 into 1 exhaust just to make sure it is not lean at WOT.

 The bike is already filthy rich. Why in the world would I go UP on the main? The 500 ran just fine with the MAC/Uni combo and 100 mains.

[matt mattison]

Matt: How did you determine it was worn?

I could tell by the way the 4 needles all fit into that bad emulsion tube. It was strictly a feel thing, and it was obvious. There is no way to take a measurement for wear in the emulsion tube. You can however take a micrometer to a known good, or new needle and compare those measurements. This way you can eliminate the needle being worn from the equation. In my case , I had only one misbehaving carb. So I could use the other good carbs needles and emulsion tubes as a reference. In your case perhaps all 4 could be bad . This is a problem less common to SOHC 4's, but it can happen. I have been told this happens to Ducati's more so. In your case, you need a new needle and emulsion tube, or a known good pair in order to make an educated guess at it.