Topic: 75 CB550 K - Dead cylinder #3 & 4- fixed 2nd and final(?) time.

[Gene]

A brief history of what's been done to my 550 lately - 3-4 months worth. Topical pieces in bold.

Sept/Oct 2016: Replaced the steering and wheel bearings, no problem. Replaced the rocker cover. My old one was "egged" out on the #1 intake valve. Rode the bike w/ minimal issues a couple of days a week commuting - for months.

December 2016: New Battery, new spark plugs, new plug caps 1 & 4 for aesthetic/purity reasons (over-head wrap-original routing). Ended up putting the previous ones back on because it seemed I had some trouble getting spark to my #2 cylinder. Turns out the #2 was not connected well, trimmed cable, reattached cap and all is well.

January 2017: New battery (gel) No real issues, still riding once or twice a week. Starter worked great for the first time in forever.

At this point the bike was running well but not optimal. I figured a new battery may help. No problems except for the fact that the new *improved* gel battery doesn't seem to retain a charge as well as the old acid battery.

Feb 2017 (yesterday): New Points, new condensers. Daichi - BUT "made in Japan" are they still sh!t? Had 'em for 3 years probably "JIC" (just in case). I was trying to figure out if somehow my charging system isn't working as well as it should because I don't have good enough pieces in the overall electrical line.

I don't know if I put the condenser wires on properly - need to check that this weekend (under/over the washer where it should be) and couldn't find an example in the manual as to where the blue/Yellow/green respective attachments go.

I plan to check connections, check timing again, check gap. If that doesn't work - replace condensers w/previous/replace points w/previous. Check fuel for #3 cylinder (cold, cold, cold).

Bike starts but won't stay running.  Getting back to it this Saturday.

I will provide pics of the current points situation soon.  This is my back-up bike these days, but it doesn't do any good to have a back-up if the back-up doesn't go.

So, not in a rush, but I think I fckud something up when it was working fine. Just wanted to get this out here.

Thanks for any theories,
Gene

[scottly]

Just for a start, what does the #3 spark plug look like?

[Duanob]

 If it's just the #3 cylinder and none of the others, you can rule out points, coil, ( 2&3 together) plugged fuel line or tap (3&4 together).

Plugged pilot jet?

Did you check spark? Maybe just a dead spark plug? bad cap connection? I had a pretty new Denso plug go bad right away so I went back to NGKs so don't rule out plugs either, even if they're new.

[chewbacca5000]

If it's just the #3 cylinder and none of the others, you can rule out points, coil, ( 2&3 together) plugged fuel line or tap (3&4 together).

Plugged pilot jet?

Did you check spark? Maybe just a dead spark plug? bad cap connection? I had a pretty new Denso plug go bad right away so I went back to NGKs so don't rule out plugs either, even if they're new.

If two is good then it is a carb issue.  These are super sensitive to the fuel level.  750s are much more forgiving.

[Gene]

I did neglect to mention, I pulled the bowls and cleaned all the jets a week ago. Ran it after and it seemed in good shape, much better. But I do intend to see if maybe the #3 float valve is stuck and that bowl isn't getting any fuel. When working upside down I may have screwed something up.

And yes, I checked for spark on each cylinder before I tried to fire it up - looked fine if maybe a little weak.

I'll pull the plugs and snap some pics.

As always, thank you gentlemen. I'll update either Friday night or Saturday with pics and any findings.

[calj737]

...and you mention replacing 1/4 plug caps, but not 2/3. Measure their resistance. If the plug (3) is pulled and its clean but wet, you have a spark issue. If its black and wet, you have a fuel issue. A dead cold cylinder tells me spark. Even without fuel, a sparking cylinder will still get warm.

[Gene]

Cal, I had replaced all four caps about a year or so ago. The ones i recently replaced were only to run the plug wire through it's original route, up over the head through the little clamp, etc. My wires a re a bit short from trimming to pull that off perfectly so I went back to the not-as-new-but-still-pretty-new caps and the routing.

I just pulled the plugs - looks to me like 2-3 are a little rich, 1-4 maybe lean? They don't look that horrible though, except 3 was a little wet. Again, I can't help but think spark.
1-4 from the left.

I reset my points gap (properly this time I think - using the F mark plus 90 degrees etc.) so we'll see.  Still working here and there. Looks like maybe the condenser wire was shorting on the points plate - I remedied that, perhaps. point pics below. Forgive the focus, I'm not a great shot.

I'm about to drain the bowls to make sure fuel is getting in there, I'll probably drop #3 just to make sure everything is in place correctly.  Get back to all on that.

Thanks for the suggestions so far gents.  Back at it.

P.s. Battery reads 12.54 at rest. I think that's right. So I don't think it's the battery. Correct me if I'm wrong.

[calj737]

If #3 is wet and slightly fouled, fuel is getting there. You have a spark problem. Simple as that. Condenser, point, wire or cap. Easy to determine.

[Gene]

Got it started. Probably Points. At least I think so. All cylinders firing, good warm compression coming out of all four exhausts as well. Think I'll give it a short test-run. Still seems to be a bit boggy at idle, might just need a run.

[Gene]

Runs like a champ for now. Thanks again fellas. Idles nicely, just needed a little "blowing out" I think.

LESSON: Don't change your points/condensers when you feel pressed for time and have a few people watching and wanting to chat. You will get distracted and miss something simple.

[Gene]

Lesson 2: Don't get so excited Mr. Smarty-pants.

Went to start it this morning - back to the same issue with a dead #3, maybe 4. Flooded out and burped gas out of the overflow(s?).

Never did take the bowls off last weekend, just checked for fuel.

I'll update when I get back to it - I have an idea it's that #3 float needle and bushing. It's the only piece I messed with other than cleaning the jets. I wouldn't be surprised to find it sitting in the bowl.

Update later. If nothing else as a warning to others.

[Imago]

I'm going with a bad resistor or plug cap on #3 cylinder, particularly as the problem is intermittent.

I spent a LONG time fighting with a similar problem in 1981 while riding my first bike, a 1975 CB550K, identical to yours, to see Mount St. Helen after it erupted. I seem to recall it was #3 cylinder, too. Coincidence?

Mine was "flake sunrise orange"!

I wish I still had it.

[Gene]

I'm going with a bad resistor or plug cap on #3 cylinder, particularly as the problem is intermittent.

I spent a LONG time fighting with a similar problem in 1981 while riding my first bike, a 1975 CB550K, to see Mount St. Helens after it erupted.

I'll certainly check the cap - shoulda done that just to rule it out. Thx.

[Imago]

I'm going with a bad resistor or plug cap on #3 cylinder, particularly as the problem is intermittent.

I spent a LONG time fighting with a similar problem in 1981 while riding my first bike, a 1975 CB550K, to see Mount St. Helens after it erupted.

I'll certainly check the cap - shoulda done that just to rule it out. Thx.

I have to give some credit to Hondaman here:

http://forums.sohc4.net/index.php?topic=67096.0

[Deltarider]

Always first doublecheck what you've worked on (as you yourself suggested btw).

[strynboen]

if the carbs is overfloting..you still have rust in the tank..vho bloks the flotvalvets..and flots the engine a bit somtime..
mine ran first real good after i kleande and accic kleaned the tank and trow the inline filter avay...after that it have run for 5 years..just have gum in the carbs one time(a easy flush..and it vas fixed)

[Imago]

Update?

[Gene]

Here's the update. Dropped the bowls on the carbs to look for issues and found none.

Replaced plug cap #3 w/new just for fun. Checked for spark on all four - good.

Checked the spark advancer, just in case, it's lubed and in good shape.

Have fuel, have spark, have air.

Started it this afternoon after going through all these things - ran like gold. UNTIL, went to wind it out a little, suddenly - in what felt (as a rider) as a flooding out, I lost power. Limped it home and now 3 & 4 are cold - only on the muffler - headers are warm because there is spark. (checked again for spark to make sure - grounded to the head, etc.).

So, as of 15 minutes ago, I have a bike that ran fine for about 20 minutes, then lost 2 cylinders.  I didn't see any gunk in the carb bowls, but my tank is not pristine. I do have a sock filter inside the tank. It could use a cleaning. Again, the bowls, jets, etc. looked good on initial inspection.

As far as I can tell I looked at everything I've done lately - new plugs, new points and condensers, cleaning the jets. I haven't gone back to the work I did replacing the rocker cover a while back, but that could be an issue (?)

At this point, I guess I'm looking for ideas.

Again, we have fuel, air, and spark - but it's weird it would be on 3 & 4 - 1 & 2 are fine.  To clarify, I am aware that 1 & 4 run on one coil; 2 & 3 on the other - (L side = 2&3, R = 1&4 - whatever - longer ones go to 1 & 4). My plug wires are actually numbered so I didn't exchange those by accident.

Checked gap on the plugs, what I haven't done is check my points again after the problem.

I'm an idiot, and willing to admit my mistakes - do I have the points/condensers hooked up wrong ? (see pic above)

P.s. - Valves?

[firebane]

You haven't stated anywhere but have you set the timing while running? Also what points gap and plug gap are you using?

Have you done any tests on your coils? Maybe they are bad and when getting warm they fail. Being 2 different cylinders means 2 diff coils acting up.

What plugs and caps are you running?

[Gene]

You haven't stated anywhere but have you set the timing while running? Also what points gap and plug gap are you using?

Have you done any tests on your coils? Maybe they are bad and when getting warm they fail. Being 2 different cylinders means 2 diff coils acting up.

What plugs and caps are you running?

NGK plugs and caps. Static timing (not stroboscopic yet).  .25" plug gap, .15" point gap.

Off to dinner.  Thank you for replying.

[firebane]

You haven't stated anywhere but have you set the timing while running? Also what points gap and plug gap are you using?

Have you done any tests on your coils? Maybe they are bad and when getting warm they fail. Being 2 different cylinders means 2 diff coils acting up.

What plugs and caps are you running?

NGK plugs and caps. Static timing (not stroboscopic yet).  .25" plug gap, .15" point gap.

Off to dinner.  Thank you for replying.

5k ohm caps and non-resistor plugs? Should be D7ES plugs and 5k NGK caps. Also plug gap should be at a minimum of 0.028

[scottly]

 headers are warm because there is spark. (checked again for spark to make sure - grounded to the head, etc.)

The headers will get warm, even with no spark, from compression. How are you checking for spark? What do the new spark plugs look like?

[Gene]

Firebane - plugs and caps are as spec'd. Did resistance testing, all in range - nothing over 5.6. Parts are as you described. Gap is in US inches, .025. Sorry, didn't list the leading zeroes on the initial post (including points).

Scottly, plug against head, visual check. Kicking, key on, switch on "run". Plugs look as pictured above - no change. Even after the fail.

It's the carbs - gotta be. It's been 3-4 years since I've pulled, inspected, cleaned. I'm hoping it's that simple.  Just odd that it would be a problem after 3-4 years trouble-free. But, we don't have a "down-time" out here in Southern Cal. So maybe it's a maintenance item I should put on my calendar once a year.

I have fuel, I have spark. Air hasn't been an issue. The only thing between the cylinder and the fuel is the carb itself. So somehow that fuel mix isn't making it there to be lit.

I will get back to this in a week or so, a lot going on right now - unfortunately non-moto related. Nothing bad, just busy.

Thank you all so far for your suggestions and checking in.

[Jimray23]

Do u have 1 or 2 fuel lines coming from the tank to the carb? The reason i ask is, if u have 2, the line going to cylinders 3- 4 maybe restricted. If so the carbs will still fill but not fast enough to keep those cylinders firing. Once u stop the carbs will fill up and look normal.

Jimmy
1979 kz1000 ltd mkii
     dyna s ignition, dyna 3 ohm coils, solid copper core plugs, full rewire.

[RAFster122s]

Swapping the coils from side to side would give you the ability to change the plug connections so the short and long swap as you won't have ability to do it without that physical movement given your earlier comment about the wire length.

Have you removed the wires on the coils electrical connect and given them a good cleaning... Removing the coils and giving their pads to the frame connection and the frame connects a good scrub isn't a bad thing to do if it has been a few years.

Voltage checks of the input to the coils with the wires disconnected to ensure
What are the ohm reading of the coils primary and secondary?
Plug caps on or off as long as consistent between the two.
Sounds like it might be a temperature dependent problem given the first start is becoming problematic after a good run the night prior. If it is running rich you could be fouling the plug in the low speed and idle time finishing your ride. Which would point to carb imbalance.

But, I first would eliminate the spark issue as 90% of carb problems are electrical.

Did you check for any leaks at the boots?...unlikely given it is wet looking...but leaks will cause running problems.