Topic: CB550 stalls while coasting

[SamP]

Another day, another discovery.

Tried syncing the carbs after swapping the jets/emulsion tubes between 1 and 4. They weren't too far off, at least enough to account for the carbon fouling. So while I was in there I decide to check the needle heights on each carb and see where they stand. Turns out they're all on the center clip of the needle. Now I know.

When putting them back I realized I didn't know which direction the slide was supposed to face (one side has a little notch cut out, and what appears to be a hole for a screw but nothing goes into it. Also, one side (front or back) has an upward taper, while the rest is flat. Problem is, it seems to fit both ways, and I don't know if I had installed it backwards on one of the carbs. Checked online and from the microfiche it looks like the slot goes on the left side so I confirmed that all were properly aligned.

Get the slides back in and installed and decide to sync again, and it's way off between 1 and 4, which makes me think I did have one or both backwards. Got it properly synced, even though it was still doing this odd sputtering every few cycles.

That's when I notice the resistor cap is arcing across #1 to the head! It's only a few months old, so I have no idea why it'd be doing that. Tried twisting the other caps into contact with the head  and they didn't seem to spark or arc at all. When I twisted the cap away from the engine enough the arcing stopped, and the little stutter that kept happening every few cycles stopped as well. Removed the caps and realized saw a lot of green corrosion in the lead. So essentially the engine is stuttering because the cap on #1 is arcing, and I don't know why it would do that. New coils or clip them and install new wires? Any help?

Other discovery - Hondaman, you are correct that my springs are annealed. I was reading through another thread where you and I believe dave were mentioning how the response just off of idle would be horrible when timed to the F mark, which is what happens to me. Really soft and sluggish in the low end in first, CONSTANT spitting back into the carb body. I tried advancing the spark a few degrees and it completely eliminated the spitting and horrible response when cracking the throttle. I know that's gonna affect the timing, but not sure how it will affect the syncing.

[Deltarider]

So essentially the engine is stuttering because the cap on #1 is arcing

As a matter of fact this is a very common and known problem with the 500/550s. I cannot stress enough to always start with the simplest and check if maybe one of the caps is arcing. Best seen in the dark. Very easy and cheap to fix and NO need to go right at all kind of complex activities inside the carbs. BTW I'm always amazed how much talk there is in this forum (compared to others) about needle positions, float heights, syncing etc. It just doesn't match with what I've seen in over 35 years and I suspect a lot of echoing. Always start with checking the ignition including the points and doublecheck! It can save you lot of nasty work. 

[SamP]

I understand your frustration - I'm right there with you and have been through this seemingly unending process. But the issue started with stalling during coasting, which really was a carb issue - it's just recently transformed into this current manifestation. And all this input has been very helpful for me, and hopefully for anyone else who finds this thread years later that has been having similar issues. For example, now I know my spark advancer needs tweaking to be optimal.
I'll probably get an answer when I try running it again with new plugs, but my question now is would the arcing at #1 draw enough current to weaken the spark in #4 to cause plug fouling? Because if it doesn't, I've still got to solve that issue.

[SamP]

Spark plug wire splicer + some fresh, new 7mm wires cured the arcing off the resistor cap. Installed a new plug in #4, synced, then went for a ride. Took out the plug and it's still fouled.

Which now means I think I've isolated it to a blocked passage in the idle circuit, since all the other plugs look fine, wires/coils don't change anything between plugs, needles and main/idle jets don't change anything. Float height is good and even across all 4. No vacuum leaks found, valves all adjusted to spec, compression good across all 4.

Any recommendations on a good dip? There seems to be contrary opinions on its efficacy, but I don't know if I can get the passages I need to get cleaned with wire alone (I'm not even sure I know where all these different internal passages lead, anyway). Otherwise not sure how I can know that all the passages are free and clear without replacing the body.

Any input on cleaning, as well as any other possible plug fouling causes I may have missed, would be appreciated.

[Tews19]

I use the GUNK. it comes in a gallon paint can. Works great. cleaned at least 4 sets of carbs in the same can.

[flybox1]

Ultrasonic, if you have access to one. 

[ANDY W]

Didn't happen to remove the idle mixture screw out of #4 carb and check for a extra o-ring up in there?

[SamP]

No extra o rings anywhere, but I did take apart #3 and #4 and do a really solid cleaning. Researched and saw that the dips weren't as foolproof as I was hoping, and opted for some carb cleaner in a can I had on hand, a lot of compressed air, and a high e string from my guitar through all the ports I could get it into. Also swapped out the slide needle holder from #4 with a new one (those are tapped out from the top down for anyone wondering how to do that - couldn't find many sources on how to swap that out. Held in place by the emulsion tube, but can get lodged in there after many years), and swapped the mixture screw/washer/o ring out between 3 and 4.

Wiped down the plug on #4 and synced. Went for a ride and you know what? Plug electrode on #4 is nice and gray, as is #3.

Thanks to everyone on the forum for all your help. Really appreciate your extensive knowledge and your willingness to share.

On to ignition timing!!!

[BudgetBiker]

This is an old post so probably wont get a response. I started with the same problem on a bike i got up in Austin. A 1975 CB550F Supersport. I have replaced, rebuilt, check so many things and still get the fine on the stand, lousy on the road issues. It will sputter to third gear and suddenly start to build speed but once in 5th it loses power and struggles. I downshift and let off the throttle a bit and then apply and will start to gain power again. Coming to a stop almost always stalls the bike. I have 110 mains and 40 pilots per classic Octane and velocity stacks. Original owner lost it and treated the bike like garbage. Found pennies in the gas tank. Carb is rebuilt. Needles set to middle notch. Replaced both coils. It has Dyna S coils of undetermined model. The rotar was on backwards and firing wrong so corrected that. Using a light to set the timing in the F mark made it worse so i adjusted by hand while it was running very carefully and improved idle but same main problem. I cleaned up some ground wires and electrical lazyness from the last owner and soldered and shrink wrapped the parts that needed it. New plugs, new rectifier, new coils, carbs re synced. But today i sprayed throttle cleaner at the intake manifold boots to the carb and it stalled while idling instead of reving up.  So too much fuel. Yet turning the A/F mixture made no difference. I replaced the o-rings where the metal intake attaches to the engine and resolved the vacuum leak. Im wondering if i need to re-sync the carbs again. I have been working on this bike for a year or more trying to get it running right. I even replaced the oil pump that leaked and the head gaskets as they had a slow oil leak as well. Replaced the clutch plates and springs. Replaced the petcock, seat, signal lights with LED, headlight with Halo LED and other none engine related parts. I have lost a lot of money at this point and i cant afford to pump anymore money into it. So after my carb sync this week, if it still has problems I'm junking the whole bike. I learned a lot and one of those lessons was that buying a bike used is the worst thing ever. My first bike which i still have runs great and i fixed it up no problem but it is an 02 Shadow spirit VT750. Same mechanics except for a computer to run the fuel pump. But this CB550F is a headache. I rebuilt the forks twice due to leaking, replaced the front brake rotor twice do to a constant squeeling, rebuilt and replaced the front brake and lines also. But the stupid spring push adjuster only stops squealing if in a perfect position. This bike has been a nightmare for me. So right now, i have this stalling problem when coming to a stop and problems keeping speed/power in 5th gear. My problem sounds a lot like the original posters and i read through every post here. But im at a loss. I even re set the valve tappets. Anyone else have any other ideas before i take a sledge hammer to this pain in my ars?

[bryanj]

110 mains is way too big for a standard 550. 100 at best