Topic: New Member - 1978 CB550 carb sync issue. Lean now, and #2 cyl not firing.

[Calvin]

LATEST UPDATE:  Watch this video to see bikes behavior when pulling plugs: 

Seems like they are all firing at this time, but #2 and #3 much less powerful than 1/4. 

2nd UPDATE: after new plugs I still have the #2 cylinder not firing or intermittently firing. It has a good bright blue spark, there's fuel in the bowl and the float height looks spot on. I am guessing it isn't getting fuel 
But it's hard for me to believe it clogged that fast after a carb rebuild.

UPDATE:  I think i found my main issue which was bad spark plugs in two cylinders after only 800 or so miles on them.  Still wanted to post this for advice and also an introduction.

Since this is my first post on this website I figured I should include a short introduction:

I have been viewing this forum for the last couple months working on my 1978 CB550, it is my 4th bike but only my first 4 cylinder carbureated one.  I have worked on all my bikes and vehicles my own, but I am still learning more about fine tuning carbs, for now, lets just assume I know nothing at all to help my learning curve with this issue.

My Bike:
1978 Honda CB550K
15,100 miles, had 13,900 2 months ago when I bought it.
Individual straight pipes
pod filters
#110 main jets
#42 slow jets
Needle setting: Not sure, whatever the PO set them to.
Pilot screw: 1.5 turns out


Basically, as the title says I have an issue syncing the carbs on my bike.  I bought the bike a couple months ago, the PO said he had the carbs jetted properly and tuned for the straight pipes on the bike, but the bike had sat a year before I bought it.  After I ran about a tank of gas through it (Looking back it was probably year old gas, had I known that I would have drained it), it started sputtering uphill and under load.  After a brief search on here it definately seemed that the slow jets were clogged, considering it idled poorly and started to stall at an idle when I gave it a little gas. 

I disassembled the carbs, put new slow jets in, the same size, gave everything a very good scrub and bath in pine sol, then cleaned again with fuel, and all new gaskets, but I ended up having to reset the float heights, the tab may have got bent during cleaning a couple floats were not getting any gas.  After forever of fiddling, I got all the floats set pretty dang even at about 1-3mm below the gasket surface.  I think I ended up having them all around 14.5mm after reading some posts and that seemed to work the best, 12.5mm left me with a couple bowls overflowing. 

After reassembly, the bike ran absolutely great except right away I noticed a pretty loud backfire out of cylinder 1 exhaust pipe.  This really only happened at slow speeds or idle especially after a long period of riding at high speed/rpm then coming to a stop light.  Either way, the bike ripped again like when I first got it.  I was basically used to this for riding:

1000 - 3000 rpm:  Average power, decent acceleration
3000 - 5000 rpm:  Pretty flat spot, not good accel even when cracking the throttle open a bit more
5000 - 7500 rpm:  Bike absolutely F*cking rips.. runs great, sounds great.

Now this brings me to my current issue....

I tried syncing the carbs with a vacuum gauge style carb sync tool.  After the first initial reading before adjustment, I noticed as I expected, cylinder #1 was way off than the rest. 

Carb sync at around 1800 rpm for first attempt:

Approximate initial readings were:
Cyl #1: 37 mmHg
Cyl #2: 15 mmHg
Cyl #3: 12 mmHg
Cyl #4: 22 mmHg

So I turned the damping knobs (just valves that cut off air) almost all the way in to get a good reading so that the analog needs was not bouncing all over the place, but that led me to wonder: Why the hell is Cyl 1 and Cyl 3 at lower rpm absolutely all over the place? I turned the rpm down to around 1200 rpm and I turned the damping valve screw back out so it was just free flowing air and the needles on #1 and #3 literally bounce from the max negative pressure reading to the positive, while cyl #2 bounced about +/- 15 mmHg and Cyl #4 was almost completely still.

I understand that at slow rpms the needle is going to react to every combustion cycle and "bounce" more, but the fact that the cylinders are way out of whack when the bike ran really pretty good given my lack of power now is perplexing me.

Anyways,  I am focusing on this issue because I synced the carbs to all be right around 18mmHg and made sure to blip the throttle after each adjusment to make sure they were all pretty equal, and now the bike idles fine but has a huge power loss.  The bike just feels very flat all over, it no longer has that nasty backfire out Cyl #1, but it feels slow, runs flat, and now still at any rpm, the bike runs flat all over.  I am not sure why after the carb sync it is running so much worse.  I adjusted all of the slides on to match cylinder #2 and all of the cylinders were withing 5mmHg of each other easily, I left the pilot mixture screws the same because thats where they were before syncing while it ran great.  But now after riding it a couple times to test it, once with the pod filters on, once with them off, the bike runs flat, and just overall like crap compared to before. 

I took a video of the most recent carb sync (link below), you can see in the video when I turn the idle screw back out to lower the rpms at around the 1 minute mark, a couple gauge fluctuate like crazy and the other two are pretty steady.  I was hoping some of the gurus on here (or just anybody that has experienced this) could chime in and maybe have some advice.

UPDATE:  I THINK THE TWO CYLINDERS THAT WERE NOT FLUCTUATING HAD NO SPARK AT THE TIME.

I dont see how I could be running overall much richer/leaner after just syncing them by adjusting the throttle slides.  I understand maybe two cylinders were rich/lean before and the other two weren't.  But I have a feeling that the issue is related to the bad fluctuation between cylinders.

I recently tried to do a compression test, but turns out my harbor freight gauges were incredibly in accurate after testing them on my air compressor (go figure,right?).  I know that will probably be a major question, but I would assume my compression is all pretty good considering how great this thing ran when I got it.



I understand this is long winded and not a great first post for these forums, but I have done a lot of reading on other threads on here and haven't found the answers I am looking for:

http://forums.sohc4.net/index.php?topic=109894.0   (most similar to my exact issue but different carbs)  bike ran worse after carb sync and carbs were way out of whack
http://forums.sohc4.net/index.php?topic=89103.0
http://forums.sohc4.net/index.php?topic=142080.0
http://forums.sohc4.net/index.php?topic=5410.0



Thanks in advance for taking the time to read this or view the video and help me out.

Hope to be posting and learning a lot more on here after this annoying issue.



******
NEW ISSUE.... when replacing all the spark plugs to D7EAs when I realized I had bad spark, I also realized I was not running the right plugs, I had D8EAs in there.  But I am not sure whether it is due to the new plugs, or the fact that I adjusted the pilot screw which used to be 1.5 turns out, I adjusted it to 1 turn out because I thought previously that it was running rich ( I realize now turning that screw in will actually richen the mixture, so make it even worse if it was rich) after the carb sync and viewing the plugs, but now it is definately running lean.  Took a short ride, very poppy, quite a bit of power, popping on decel and sometimes missing or not firing around 3k rpm.  I also right after new plugs ran it on the straight away on my road at about 1/4 to 1/2 throttle around 4k rpm for 30 seconds then killed it and coasted in to my driveway to view the plugs.  They were very light, looked like it was running very lean as I would expect.  It looks like my next step is going to be to richen that mixure screw and turn it in even more.

Still would like advice on this if nobody minds ^^

Thanks!

CARB SYNC VIDEO:

[Calvin]

Bump

[calj737]

A couple of things:
You really need to verify the needle clip position to aide in your tuning.
Only change 1 thing at a time as you tune. Too many differences impede understanding of "which change" made the difference.
Have you verified your ignition timing?
Have you adjusted your valves? This could easily contribute to abnormal vacuum results in #1.
Pods and straight pipes make for pretty tough tuning, so buckle up for a while as you burn through plug chops.

Start with a fresh set of plugs, and do an IDLE chop. Get that right. Then go for a WOT chop. Get that really close. Then tinker with the needles, then the screws as a final "tweak". But verify your timing/ignition health and valves first.

[flybox1]

The # reading on your vacuum sync tool is irrelevant.  you want ALL your carbs to read the same value (sync gauges calibrated?)
Check off the following.
Clear tube check your bowl fuel level and adjust floats as needed to get 3mm below the top of the bowl
Meter you plug caps for resistance (ohms) and report your findings (use D7EA plugs)
What brand jets did you use in the carb rebuild?
valves adjusted and static timing done?
+1 - new set of D7EA plugs and start the bike.  Let it idle (no throttle) for 4-5 minutes (fan on the engine) and post a picture of the plug tips for us to see.

[Bankerdanny]

The carbs on the '78 bikes have the leanest stock settings of all the 550's, an issue you compound with straight pipes and pods. My personal opinion is that you will always be lean with this setup and the best you can do is pick what part of the rev range that situation is the worst.

[Calvin]

So currently I am still troubleshooting the issue on the fact that the #2 cylinder isn't firing, either all of the time or at all.  I just have not had time to get a good compression tester yet to see if it is lower than the other 3 cylinders.  I am very confident that it has good spark, at least at idle speed, which is when it is not firing.  I just want to check compression before I pull off the carbs again to clean them and make sure that it is getting fuel.  The bowl for that cylinder is full of gas and equal to the rest, so it could be a plugged jet. 

So to your comment Bankerdanny, would you at all recommend going bigger than the stock #42 slow jets?  The mains #110 I think are fine because it does not pop as much or at all at full throttle and runs perfect with it wide open.  As far as the pilot jet/needle goes I thought the needle setting was perfect when I got the bike, but since I went to the hotter plug I have a feeling I might need to change that needle setting to enrichen it a little bit.

Flybox,  I will do the plug test and idle for 5 minutes and post.  I basically did this last time but I did not check at idle.  I put brand new plugs in, rode it down my road and back around half throttle then killed it and coasted in and the 3 plugs that were firing all looked white/gray and lean (to my not expertly trained eyes) and the #2 cylinder almost looked new just like when I pulled it out of the box, im sure due to the fact that that cylinder wasnt firing.

I have done the clear tube and have pictures of each bowl, they are all 1-3mm below the gasket surface. 

Have not checked plug cap resistance yet, (nor have I ever done this, I will search on here where to measure resistance). 

The slow jets I know are Keihin jets, I put those in.  I will check the mains and pilot jets also, I want to do the compression test before taking my carbs off again.

Timing was ''just done" by the honda shop before I got it according to the PO.  I believe him, and I have only looked at the points to verify how the points looked because he said the points and condensers were just replace and timed by the honda shop, the points did look very new.  I believe the timing is good, I can check that last.  Right now, I want to get #2 firing.


Thank you guys for the help, I will follow up with compression #s and also spark plug pictures at idle for 5 mins with new plugs.

[flybox1]

Trusting of you to assume the PO told you the whole truth, and nothing but the truth. 

[Calvin]

I understand you would basically take nothing as truth if a PO said it. I understand, same here. Like I said, I will check the timing last because along with the receipt of work he showed me, I checked the other things get said the honda shop did and sure enough, it was done. I would assume the timing is not the issue because the other cylinders are firing perfectly fine and the bike still has plenty of power. So I have no reason to start there.

[scottly]

Please post pics of your spark plugs after riding the bike, not after idling for 5 minutes.

[alacrity]

What needles are in it? What position are they in? Are the emulsion tubes clean and clear in each carb identically?

[RAFster122s]

If you have aftermarket brass in, likely, instead of genuine Keihin, then you are likely to apples and oranges in your carbs...  If the original jets in the carbs were Keihin, then clean them and put them back in.

You really need to pull the carbs to see what alacrity said... Just so you know you have clean jets and the needles are all in the same clip and the needles are straight (on the off chance one could be bent...)
You will also know what condition the elmulsion tubes are in... If there are any jets that have wear due to corrosion, then they need replaced.  They should look the same between carbs...slow jets all the same and main jets all the same.  Then there is an off chance a PO has drilled the jets, which can really cause you to scratch your head in disbelieve and frustration.

Start with the basics like Cal said, verify the 3000 mile tune up is correct. Ask questions to help you through it if you don't know how to do it on the cb550.  The shop manual and service instructions are available for download off the sohc/4 sites...
Parts manuals too...

David

[alacrity]

++++ many 1's   What you are doing here, Calvin, is akin to walking up to a big tree with a single shotgun load and aiming into the leaves in the hope you'll hit the pheasant.  Imagine if you could REMOVE the leaves blocking your view of the branches. Your target would be clear.

Remove the leaves, grasshopper.  Don't guess. Don't hope. Don't try pieces of different solutions.  EVEN IF you find your carbs are perfect and the problem (or problems are elsewhere), you will now be certain of what your 4 carbs have in them and the long list of variables will now become one single constant truth: Carbs are good to go.  So after this, you can always just look elsewhere for any performance problems (for the foreseeable future, assuming you don't suck some sort of crap into them).
 

[Calvin]

Thank you guys for all of the advice. I understand I posted a lengthy post with an issue during syncing my carbs. Just to restate since I have seen a few people ask what's in the carbs and to tear them out..

Cylinder 2 is not firing at idle. It has spark. That carb bowl is full of gas. So I believe I am either missing compression or fuel, possibly a clogged jet.

I want to check compression first.

I JUST got some rebuilding the carbs 1 month ago when it started sputtering. I put brand new #42 Keihin slow jets in it  it had #110 keihin main jets, definately not drilled.

I replaced all the gaskets, o rings, and cleaned everything thoroughly. It ran great after a rebuild.

Now, it is not firing on #2. The difference now is i replaced the plugs with D7EAs and now I noticed it is running leaner and also not firing.

I will get compression #s shortly and also plug pictures.

[calj737]

D7's burn hotter than D8's, so thats no surprise. Its more likely a clogged idle circuit than a compression issue since you say the bike behaves above half throttle.

[Calvin]

Thanks calj737! That makes sense and I hope you're right. I still have to do a compression test for my own sanity ( I'm partially hoping for slightly low compression for an excuse to do a rebuild)  but I will be sure to update shortly for the sake of everybody that's helped out so far on this issue.

Many thanks.

[scottly]

Slightly low compression can be caused by incorrect valve adjustment, so rule that out before opening the can of worms that a rebuild always brings on.

[RAFster122s]

So, to rule out the cylinder not dropping out because of a valve adjustment issue, then performing a 3000 mile maintenance that includes adjusting the valves would rule out that cylinder having incorrect valve adjustment. Like Scottly said and I think others have said...


Then, if you still have the running issue, then pull the compression readings.  A good quality compression gauge without a long hose and that has the check valve (one way valve) in the adapter before the hose is better than the run of the mill cheap gauge.
Here's a YouTube on checking Spark, Fuel, and Compression.  It should be useful.

Here's Matt's review of a good MC Compression gauge by Actron
It give him good solid numbers, not true for a lot of compression testers out there...

It is good to have a baseline reading for your motor, but really it is wasted effort to do it before checking the valves. Because you will do the compression test twice. You will know from checking them if they are out and you can adjust them properly. A tight valve adjustment isn't a good thing... Loose valves (within the spec) don't burn valves.  As far as doing it twice you will see if it improves but, I think it is better to just set them and then test. I'm in that camp.

Hope these help.

David

[Calvin]

Compression Test:

I warmed the bike up to riding temperature, made sure the choke and throttle was wide open, and had all the plugs out and did a new compression test with a better, non harbor freight tester.

The cylinders from #1 to #4 were:

138/125/143/130

From my previous post, it seems that #2 cylinder is not firing, at least not at idle.  When I open it up, it feels fast and I believe that they are all firing.  As suggested, I took pictures of brand new plugs after riding for 5 minutes right after the compression test.  But first, here are some pictures of the plugs that were in it, which only had about 3 miles on them.  I put them in, took it for a short ride, it felt like #$%*, then I began digging into it.




As you can see it looks like #1 and #4 were very rich, and #2 (the problem) and #3 are very lean.

Each one has the same setting for the pilot screw, 1.5 turns out.

Still don't know the needle setting, yes, I know I need to find that out.



Here is a picture of brand new plugs I just put in after the compression test, the bike was already warmed up, It fired right up, then I took it for a 5-10 minute ride trying to keep it in the range so only the slow jets and pilot jets were being used.  I tried to keep it around 1/3 throttle, definately didnt go much over 1/2 throttle if any.

New plugs:



Pretty much same result.  Not entirely sure why the plugs are so different with the same settings, I think the obvious answer is some clogged jets in #2 and #3 but this post is for all those that have taken their time on here to respond, which I appreciate a ton. 

Also, I do realize that the cylinder with intermittent or no firing is the one with the lowest compression.  Sounds like checking the valve adjustment will be next.  Also, I have verified that they all have good spark, I have swapped wires and plugs and made sure that each one has spark.  When swapping wires 2 and 3, cylinder #3 still fires but #2 would still not fire at idle.

[flybox1]

... it seems that #2 cylinder is not firing, at least not at idle.  When I open it up, it feels fast and I believe that they are all firing.

^^^ an indication (to me anyways) there is something preventing gas flow in the idle/pilot jet circuit in that carb.
When you 'open it up' you involve your needle jet/main jet in supplying fuel to your engine.

[Calvin]

... it seems that #2 cylinder is not firing, at least not at idle.  When I open it up, it feels fast and I believe that they are all firing.

^^^ an indication (to me anyways) there is something preventing gas flow in the idle/pilot jet circuit in that carb.
When you 'open it up' you involve your needle jet/main jet in supplying fuel to your engine.

Thanks, thats what I have been wondering/thinking.  Any feedback on the spark plugs?

[flybox1]

I would suggest going LEANER with your IMS on 1&4, by 1/4 turn.  Leave 2&3 as they are.
AFTER you adequately clean your jets and emulsion tubes (visually inspect all the thru-holes for blockage), and spray carb cleaner/air through all passageways, do a simple idle plug chop with new plugs.  5 min idle, under a box fan. 
Post pictures of the plugs before you do any butt-dyno testing out on the road.

[calj737]

I would suggest going LEANER with your IMS on 1&4, by 1/4 turn.  Leave 2&3 as they are.
AFTER you adequately clean your jets and emulsion tubes (visually inspect all the thru-holes for blockage), and spray carb cleaner/air through all passageways, do a simple idle plug chop with new plugs.  5 min idle, under a box fan. 
Post pictures of the plugs before you do any butt-dyno testing out on the road.

If I could, Fly, I wouldn't change ANYTHING yet. First, resolve the fuel delivery to #2 and also inspect #3. If they are both resolved, then all 4 cylinders should register similarly. Once you're there, then its time to start tuning all 4 together.

[flybox1]

OOOohhkay!    

[alacrity]

Forgive me if I missed this Calvin...  Does your number 2 plug smell like gasoline?  Did you swap the #2 and #3 coil leads? IF not, try it.  AND if #2 is now good and #3 is bad, there's your prob.

[flybox1]

He did swap coil wires.  no change.