Topic: 1975 CB550K spark issue

[Hillsdale Slim]

I read these forums often but rarely post.  I have had my CB550 since July and am still getting it into true running condition. I re-started my motorcycle hobby 4 years ago which I quit doing in 1972. I wrench as much as I ride. This has me stumped: Cylinder #4 does not seem to be firing or pulling. The carbs, electrical, valve adjustments have all been addressed. New coils in August. When I touch the spark plug to ground there seems to be no spark. When the plug gets close to ground there is a visible spark. The other 3 plugs behave normally.
I will try to post a short video. Do I have a (brand new) bad coil?
Thanks in advance to helpful input.
https://drive.google.com/open?id=1y8Vmlhzz3r2b5CJBLrVzieoxtVpG5YKY

[BenelliSEI]

Slim..... #1 and #4 plug get fired by the same points/ condenser and coil. It’s called “wasted spark”, those pistons hit top dead centre together, every revolution. The system doesn’t identify the compression stroke, just fires every time (apologies if you already knew this).

So if #1 plug is firing cleanly, the only difference is the port on the coil, wire, cap and plug. Try swapping the plug leads.  Does the problem move to #1? Then inspect the end caps. Cut some cable off and screw it in again. Firing? Try swapping just the spark plugs? NGK plugs are not what they use to be. Lots of issues with even a new plug. I’ve had some the spark when grounded, but quit working in actual use, after a few seconds!

Finally...... could your new coil have an internal problem? Try an old one........ test one thing at a time and you will solve it. Good Luck.

[Hillsdale Slim]

Thank you Benelli.  I needed an outside view!  I hadn't thought of the switching the plug wires, which is clever! I had done all of the other things you mentioned. I did trim the wire and re-did the cap install. The spark became more apparent. When I switched plug wires the problem remained.  Number 1 cylinder working but when you lift the plug wire off of number 4 there is no effect. So now I am back to the carbs which have been off of the bike 4 times! (This is the first four carb bike I have worked on). Since everything else has been cleaned or replaced, this must be down to something like a sticking float. I have not replaced the floats. Thanks again for your tips. I believe I am on the right troubleshooting path now.

[scottly]

What does the #4 spark plug look like? Is it black and sooty? Wet with gas?

[Hillsdale Slim]

It is somewhat blackened and it is new very recently. However, all four plugs were black and sooty before I replaced them. So I lowered the needles from 2nd position to 4th position. Then it seemed too lean (backfire) so I moved the needles to the 3rd (middle) position. I was hoping I had discovered an ignition problem but it looks like I am back to fuel. I am thinking that I have been running on three cylinders since I got the bike running in late July. Carb #4 was not working when I got the bike because it had a wrinkled float bowl gasket which had constantly leaked. 

[bryanj]

Just confirm what carbs you have for me, easiest way is describe the top cover

[Deltarider]

When I touch the spark plug to ground there seems to be no spark. When the plug gets close to ground there is a visible spark.

I'd first experiment with rerouting the HTleads. Is that one of the 2&3 HT leads, tied together with an 1&4 one (red band)? That should not be. Check all 4 HT leads have some distance to one another and certainly do not tie them to the frame or even the head.

[bryanj]

If there is no spark with plug grounded but spark when held a bit away i dont care how new the plug is its duff

[Deltarider]

If there is no spark with plug grounded but spark when held a bit away i dont care how new the plug is its duff

That's what I thought, but still I'd first route the cables correctly. Tied like shown in the vid, ther might be interference.

[Scott S]

 Where is the mixture screw setting on that carb? Does that pipe get hot if you ride  the bike and get it off the idle circuit?

[Scott S]

 And just watched the video. A few observations:

 - Your plug wires are way too long. I wouldn't zip tie them together, nor to the frame. Is that what I'm seeing in the video? If so, trim them back to the proper length.

 - When checking the spark, just leave the plug in the cap and ground it on the head. Are you sure the cap is screwed on to the wire tightly?

 - You mention changing needle clip position. What intake? Stock air box?

[Hillsdale Slim]

Lots of good input here. I want it to be a spark issue because (for me) it's easier to fix. Yes, the wires are zip tied with the opposite firing cylinders. In the fall I noticed two of them were melting on the exhaust. I will move them away from the frame and each other. Here is a pic of my carbs, which I believe are the older versions. 022A stamped on the sides. I will run it again and check for a cool exhaust manifold on #4. It usually pops pretty good when trying to accelerate past 3500 or so. For now I assume that it is #4 popping. Before this, I was changing the needle position in order to address the popping. Which is a waste of time if there is a spark/ignition problem.

[bryanj]

Yes at least your carbs are not the horrible PD type, which shouldny be on there anyway but you never know what a po has done!

[Scott S]

 I can see in the pic that the carb(s) not fully seated in the manifold.

 Mixture screw settings?

 Pods or stock airbox?

[bryanj]

Thats the airbox side not on properly, probably due a new set

[Hillsdale Slim]

The airbox is stock, the idle air screw is out 1 turn, and the airbox boots don't fit on there perfectly anymore. I have changed plugs with known working plugs twice. Progress-I shortened all of the pug wires and re-tested the bike. On idle for several minutes the #4 manifold stays cool while the other three were hot to the touch. So I test rode my 15 minute route which includes a nice hill. I always rev the bike up to 7000 rpm in 2nd and 3rd gears up the hill.  2nd gear was ok but 3rd gear started popping around 6000 rpm. When letting off on the throttle, it is slow to rev back down. When I parked I tested the manifolds with my gloves on.  #4 was hot but the other three would start burning the leather on the gloves.

[Hillsdale Slim]

Update.  I bent the float tab slightly to raise the fuel level on carb 4. The bike runs much better. No popping when I rev it up in 3rd and 4th gear. It's still is slow to rev down to idle but not nearly as bad as before. The manifold is hot but not as hot as the other three. This all leads me to believe that I need to adjust all of the float levels for the actual level of fuel rather than the static measure-the-float distance method. In the past I have gotten by with approximate float levels.  Thanks to everybody who chimed in here. I am pretty confident that my spark issue is mostly a fuel issue. Time to take the carbs off again!

[Deltarider]

A wrong float is seldom the case. Floats that have been tampered with, are many though in this forum. Don't get me wrong: there's nothing wrong with checking, but an error doing the clear tube method is easily made. It takes quite some time and you have to manoevre the tube up and down to come to a reliable presentation of the fuel level inside, so take your time. The method Honda describes in the manual is a good one, provided you have genuine Honda floats, valves and needles. When you prefer the clear view method, be aware that a low fuel level can have a variety of causes. I suggest you check it with the engine running and... no, the engine will not overheat, not in the minutes it takes.
BTW, I still think what you've described, is an electrical issue.

[bryanj]

You can buy just the rubbers for airbox to carb now from places like Dave Silver, well worth doing.

DO NOT be tempted to use "Jubilee Clips" they are too wide and actually cause air leaks

[Tom C]

Slim - I recently had a similar issue with my 74CB550 with the same 022A carb bank as yours.  On my bike it was cylinder #3 that had a problem.  I first thought it was a spark issue as the plug cap resistances were way off between cylinders #2 and #3, which can cause uneven spark delivery between the two plugs connected to that ignition coil.  I decided to completely replace the coils and caps.  When I did so I still had the dirty plug on cylinder #3 only, the remaining plugs were fine.....

I replaced the rubber intake boots, removed the intake manifold and replaced the o-rings to eliminate the possibility of an intake air leak causing my problem on cylinder #3.  No change in #3 plug, still fouling.....

Re reading Hondaman's book chapter on carbs, he speaks of a problem caused by partial blockage of the air passage to the emulsifier tubes.  On our bikes that passage looks like this:


...so off with the carb bank yet again to investigate further. 
When I shot the carb cleaner into that passage on the #3 carb, it shot right back out into my eye!  (don't let this happen to you).  The other carbs had a clear path for the cleaner into the main jet cavity where the emulsifier tube sits.   I had not been thorough enough in my previous carb cleanings....damn. 

I used small diameter wire and the smallest size welding torch nozzle cleaner to clear out the passageway on carb #3 and the rest of the carbs for good measure, following up with more carb cleaner.   When I buttoned her back up and went for ride afterwards, it was like riding a completely different bike - one with 4 working cylinders instead of 3!   It was a good day, let me tell you! 

Apparently if that air passageway to the emulsifier tube is blocked there is poor mixing of the air/fuel, which does not burn well, resulting in plug fouling.   I had only the #3 carb with this problem so the fouled plug only on the #3 cylinder. 

So my point is that perhaps your spark problem is not really a spark problem at all, which I think you already know.  It might be an intake air leak or it might be a blockage of the air passage to the emulsifier tube.  Or something else..... 

Check those air passages to the emulsifier tubes - again.   It sure made a big difference in my 550 with the same carbs as yours. 

Good luck!

[Deltarider]

Tom C, what you've experienced is very rare and makes me wonder what airfilter you run, if any.
Slim, what you've shown in your vid in the OP is clearly an electrical issue. I don't know if there are any other issues. To avoid insanity, fix one thing at a time, test and then go to the next.

[Hillsdale Slim]

Deltarider- I switched wire 1 and wire 4 but got identical results. Then I replaced plug 4 again and still got the same results. As good as I feel like I am a troubleshooting, your point is still right on. Fix one thing at a time. The emotions can cloud my judgement when the frustrations start to set in. 
Tom C - you mentioned something about the carb that is helpful.
When I got the bike carb 4 was full of crud. I have squirted carb cleaner into that hole and it did come out of the needle and jet. I had the carbs off yesterday and checked/cleaned things again. I static adjusted the balance on carb 4 again, which was lower than the other 3. Even though I have balanced the carbs with vacuum gauges recently.  On my test ride the engine seemed full on after 5000 rpm. Not perfect between 3k and 4k and still uneven getting back to idle. The exhaust manifolds were about the same temperature.  So I am thinking that getting the carbs truly balanced is the next step.