Topic: 1976 CB550F -- stock coil failure?

[Hondawggie]

My bike's #1 and #4 cylinders fire consistently.

But #2 and #3 fire intermittently.

I don't have a header temp gauge -- will be buying one tomorrow.
But headers #2 and #3 are *much* cooler than #1 and #4 by way of the 'water/sizzle' test.

The points -- I verified clean, and gapped correctly.

The NGK D7EA plugs are brand new. 

I swapped #1 and #2 plugs -- no change. 




So after searching for "bad coil" here and reading lots of posts I haven't found one that explains how to swap the #1, #4 coil with the #2, #3 coil.

Seems like it should be easy:  a yellow wire on one coil from the points, and a blue wire on the other coil from the other set of points.

However this is the 1st time I've ever 'swapped coils'.

My question:  if I swap the yellow wire and the blue wire, is this the correct way to connect to the spark plugs?

- put #2's plug cap on cylinder #1
- put #3's plug cap on cylinder #4
- put #1's plug cap on cylinder #2
- put #4's plug cap on cylinder #3

Correct?

[Frostyboy]

That sounds like it would work but coil failures I think are few & far between. Of course that doesn't mean it isn't the case.
Might I suggest however that there's a couple of things to consider before blaming the coil.
Try swapping the condensors over & see if the misfire changes to the other set of plugs.
Measure the resistance of your plug caps to be sure they're not faulty.
When you have the caps off the leads, trim ¼" off the leads before reattaching the caps.
I remember my 550 had a problem with the leads leaking onto the head cover. Try running the engine with the tank off in the dark & look for lightning bolts out of the leads to ground.

[Deltarider]

Frostyboy gave good advice. Coils rarely fail, condensors do. Looking for sparks flying from caps/HT leads to ground (best seen in the dark) should be a routine with these bikes. There are two more and also easy checks anyone can do.
Condensors (aka capacitors). When idling look for possible arcing between the breakerpoints. Some tiny sparks are OK.
For clarification see this video.

In this video left condensor (1+4) is bad and causes arcing which means little or no spark at plugs 1+4. Right condensor (2+3) shows only very little sparks and is good. When in doubt, replace. Condensors are cheap. When you fit one, pay attention to the following.
Whilst you're there have a close look at the breakerpoints. Check carefully none of the connectors at the breakerpoints is too close to the plate and so can make ground intermittently when engine vibrates. Failure of a breakerpoint or condensor would affect two cilinders, 1+4 or 2+3.

[Ereyer]

I swapped my stock coils because the spark plug wires disintegrated when I pulled a plug wire off a plug.
Just FYI, I got replacement aftermarket coils from 4in1 and, although the setup is a bit different, they provide wires to connect the yellow/black leads and mounting hardware.
Haven't tried the coils yet as a carb rebuild was done simultaneously.

Almost ready to try to get the bike started.

Eric

[Hondawggie]

Thanks for the recommendations -- as I read prior posts before I posted my thread here, one person said "Daiichi condensors are unreliable/low quality and if you buy off Ebay, sellers don't often disclose the brand they're selling" -- so I'm thinking I gotta pay top dollar and buy actual OEM from the Honda dealer here?  The dealer is almost always way higher $$ than anywhere else -- any suggestions for sourcing non-Daichi  points/condensers besides the dealer?

I'm gonna try the coil swap first but in reading your advice I'm agreeing, coils rarely fail, no moving parts.  Points can fail.

[Calvin]

I am currently fighting with an issue with my 78 550K and it seems like I do have a bad coil.  Try measuring the resistance of the primary coil on each of your coils.  It should be measuring between the blue and black/white wire for one coil, then the yellow wire and black/white wire on the other coil. 

EDIT:  I took a bad measurement. My coil may be fine but if you measure yours make sure your kill switch is on.

Mine was supposed to be 5 ohms for the stock coils and one of them was 1.2 ohms.  This was the coil that was only intermittently firing for cylinders #2 and #3.

Good luck.

[Hondawggie]

Okay, here's what I read on the Primary and Secondary windings of the 2 coils.

#1 and #4 coil
- 4.4 ohms on the primary winding
- 14.4k ohms on the secondary winding (measured by connecting the ohmmeter to the #1 and #4 spark plug wires and reading the ohmns across them, which I believe is the secondary winding of the coil)


#2 and #3 coil
- 4.4 ohms on the primary
- 14.6k ohms on the secondary


So it's looking okay for the coils. 

Another possible partial cause:  when I removed and cleaned the carbs, the main jet was the correct stock size (105 if I recall) on all 4 carbs, and so were all 4 pilots, at least according to the CB550 Haynes manual.


Well, the carbs have individual pod filters and it looks like the bike's running lean.  The stock exhaust system seems loud to me, so maybe a prior owner gutted the muffler a bit?

I have coming in a couple days a complete stock airbox system for my '76 cb550F and am waiting to buy new points until after the stock air intake system is back on.


But 'too much air flow' from the pod filters, I'm not sure that explains why only #2 and #3 are only firing intermittently.

[calj737]

Your issue with the plugs firing is the condensers, as previously stated. The 105 main jet is not stock, its upsized for the pods. When you swap back to an airbox, you'll very likely need to jet back down to 98/100.

[Duanob]

Frostyboy gave good advice. Coils rarely fail, condensors do.

For once, I agree with Delta.

[Hondawggie]

Solved the intermittent firing of cylinders #2 and #3.

I was waiting for a stock  CB550F airbox to arrive after buying a complete set on Ebay.


The bike as I bought it had individual pod filters.


With the stock airbox on, it's running good on all 4 cylinders.   And I my main jets are 100 not 105, my carb rebuild kits included a #90, a #100, and a #125 main jets.

I suspected that the stock airbox *could* fix my inconsistent cylinder firing problem -- because the way the bike was running, it reminded me of "lean lurch" when a cylinder is *barely* getting enough gas to fire every once in a while.   Last time I had lean lurch was an under-jetted Kawasaki S3-400 triple; the way my cb550f was running, kinda reminded me of that, so I was hopeful returning the stock intake system would help, and it did.  That's why I didn't go out and buy new points/condensers, I wanted to eliminate the chance it was just running lean.


The original main jets that came in the bike as I bought it were #100's.   So I put the #100's that came with the carb rebuild kits in the carbs.


The plugs however show the engine is still running a bit lean.   

If as I suspect the prior owner de-restricted the stock muffler (reason I suspect that:  it's louder that normal for a fully stock cb550 exhaust) --

-- would the reduction in back pressure in the partly de-restricted muffler result in lean-looking plugs and the chrome header pipes blueing (ie. running too hot) ?

[calj737]

a more open exhaust and pods will lean the air/fuel mixture, but, I would doubt very seriously they are the cause of an intermittent firing cylinder. Spark, not fuel is intermittent. Fuel is either sufficient, insufficient, or too much.

[Hondawggie]

a more open exhaust and pods will lean the air/fuel mixture, but, I would doubt very seriously they are the cause of an intermittent firing cylinder. Spark, not fuel is intermittent. Fuel is either sufficient, insufficient, or too much.

I'm at sea level, and I may just need to bump up the mains from #100 to #110 or so.   The bike's running on all 4, after I got rid of the pods and installed the stock airbox.

It's just that the plugs are a bit too light-colored, not golden-brown, on all 4 cylinders.

[calj737]

With a stock airbox and open exhaust, I doubt 110's are needed, especially at sea level where the air is more dense. Better to check your carb settings on the needle clips and air screws.

[Hondawggie]

With a stock airbox and open exhaust, I doubt 110's are needed, especially at sea level where the air is more dense. Better to check your carb settings on the needle clips and air screws.

Okay -- seems reasonable, easy to check too -- thanks.