Topic: CB550 No Spark?

[joeyrobots]

So I have a 1975 CB550K. Last weekend it ran totally fine.  Today I went out and was kicking away like a madman to get it started, and it did start and idle for a few seconds, but died while I was putting my helmet on. After that I tried and tried and tried but could not get it to start. Eventually I realized it didn't seem to be firing correctly, I could hear compression but no sputtering.  So I pulled the plugs, no spark on any of them. Then I checked the points, no spark there either. When I crossed the points with a screwdriver, no sparking. I checked the 15A fuse, and its intact. I tested continuity across the points, and get 12V. So then I tested continuity from the yellow and blue coil wires to the black/white coil wires, again 12V.

Is there something else I should check? Any idea why I wouldn't get spark at both the points and the plugs even though it seems I have continuity? Doesn't seem to add up. The top end was just rebuilt and its been running like a dream.

Thanks for your advice.

[Mantree]

The switch on the handlebars cuts 12v to the coil then it grounds through the points I'd check 12v on the black wire coming in to the coil

Sent from my ME302KL using Tapatalk

[joeyrobots]

I have continuity on the yellow and blue wires coming from the points to the black/white wires coming from the kill switch. I checked them from the yellow and blue before it goes into the coils direct to the junction of the B/W wires before they head to the kill switch. Am I checking that right?

[joeyrobots]

I just double checked. Definitely have 12V continuity going through the coils from the blue and yellow wires before they enter the coil to the B/W wires where they exit the coil. So i believe that eliminates a kill switch issue. And I have 12V going through the points. So why on earth don't I have spark, both at the points and at the plugs?

[joeyrobots]

Ok so I just went through and checked everything throughly. I have continuity across the whole system. Fuse, Coils, Points. Checked the B/W wire across the kill switch in the headlight bucket even. So then I pulled the plugs and I was getting spark on all of them!! Nice bright blue spark

But when checking the last plug, the the bike suddenly made a loud metallic sounding pop, and I stopped getting spark. After a few minutes for whatever reason, I started getting spark again, and it remained consistent. Very strange. But then even with consistent spark, I couldn't get it to turn over. It did run today for about 45seconds, so Im beginning to think I have some other weird issue. Maybe bad fuel? We have been having a lot of weather changes, hot, cold, hot, cold here. But still starting it has never ever given me this much trouble. I'm recharging the battery as I ran it all the way down, but am going to give it another go in the morning.

[mrfish2]

Intermittent spark can usually be traced to a bad connection somewhere. I would go through with some steel wool and dielectric grease and clean all the bullet connectors, maybe that will get you somewhere.

[joeyrobots]

So i pulled all the plugs and replaced them. Checked compression in the meantime. 120 on all cylinders fully cold at 50 degrees outside. I drained the gas tank and the float bowls and put new gas in. Rechecked all the plugs for spark, which they have.

Then I went to kick it. This was the most promising that its been. Started to sputter a bit, but then just started giving me loud backfires. One single loud backfire every few kicks. But no starting. hmmmmmmmmm.

[calj737]

That would point towards a timing issue. Have you inadvertently swapped the Blue and Yellow wires around? Stock, Blue serves coil for 1/4 cylinders and Yellow for cylinders 2/3.

[joeyrobots]

Stupid me. In servicing I swapped 1 and 2 plug wires. Corrected that.

Now its not backfiring, but it still won't take.

[calj737]

Are the plugs wet or dry?

[joeyrobots]

They are wet.

Since I corrected my idiot move with the plugs, I've still been getting small backfires. But not the loud pinging ones from the crossed wires. These are more coughing pops of it wanting to go, but not quite getting there.

[Restoration Fan]

So now you're getting spark on all 4 plugs?  If so, then the problem is either one of timing or one of fuel/air.

If you're getting spark, try pulling the air box ( or pods if you have those) off.  Set to full choke and confirm visually (since you can now see them) that the floats are completely closed.

Make sure your gas is on.  Test to make sure you have gas in all 4 float bowls.

Make sure to hold in your clutch in case you have the clutch switch.  I don't know if the 550's have the kickstand switch but you should confirm that your kickstand is fully up as well, just in case.

Confirm engine cutoff switch is set to run.

Now try kicking it and see if you get any different results.

[calj737]

Well if the plugs are wet, then you have fuel, but a spark problem. Are they wet and fouled, or wet and clean?

I suspect you have an issue with your condensers, but let's eliminate some other items first.

[joeyrobots]

Hmmmm. That seems to make sense. The engine and carbs should be good unless something failed, but nothing seems to indicate that. The top end was just rebuilt, and carbs thoroughly cleaned. Air should be good, I have new rubber boots on the original airbox, with a foam filter replacement for the old paper filter. Everything was running perfectly until last weekend, when it was a little reluctant to start, which I thought was just the cold. Yesterday it turned over once and then quit, now I can't get it to go.

I put new plugs in today and still couldn't get it to turn over. The old plugs were carbon fouled, but not terribly. It did seem the 1-4 spark was stronger than the 2-3 spark. Also i noticed that I get a few promising kicks before i just get no response. Wait a few minutes and the same thing, few sputters, then unresponsive.

The plug wires have always been a bit suspect. 1-4 seem original, but at some point some part of 2-3 seems to have been replaced, probably the coil. The plug wires are spliced in to the coil wires rather than continuous to the coil. The sheathing on one of those spliced wires is pretty deteriorated, all gooey.

I think what i'm going to do is something I've wanted to for a while, swap in an electronic ignition with new coils and wires. After having to rebuild the top end this summer, the maintenance/riding ratio is skewed in a way that is testing my patience this season, and it just seems easier.

The condensers were swapped out a year ago just as part of points servicing. Two years ago the old rectifier was bad and was swapped for an oregonmotorsports rectifier. Because of new lower profile turn signals installed this season, the entire wiring harness was checked out, all connections pulled, sanded, dielectric greased, and reconnected. The clutch switch had been yanked out years ago but never had any impact, so in going through the birds nest I just pulled the wires and bypassed it.

Thanks for all your advice. I will update.

[mrfish2]

Are you sure all connections are secure? As in have you physically pulled each bullet connector apart going from the points to the coils and then re-connected them hearing/feeling them snap into place?

I'm thinking about 2 wires specifically, the yellow and blue wires coming from the points to where they connect into the main harness right beside the rear brake light switch. There should be a rubber dust cover covering up the connections there. It's possible the bullet connectors could have come loose at that point, causing your no spark condition. Go ahead, ask me how I know to check there... 

[calj737]

I put new plugs in today and still couldn't get it to turn over. The old plugs were carbon fouled, but not terribly. It did seem the 1-4 spark was stronger than the 2-3 spark. Also i noticed that I get a few promising kicks before i just get no response. Wait a few minutes and the same thing, few sputters, then unresponsive.

Okay, so I am confused. Your plugs are carbon fouled which would indicate a very rich condition, too much fuel against a weak spark. But you said they were wet too? Thats another indication of too weak a spark to burn the fuel present.

If, you are 100% confident that the carbs are properly set up (based upon them working, riding and behaving normally 2 weeks ago) and suddenly you have ignition issues, then simply replace the points AND condensers. This is the most logical and inexpensive solution. It should take less than 1 hour and it will confirm tons of presumptions.

Replacing the coils/wires sounds as though it might be prudent after you first sort out the ignition plate. Do NOT buy Daichi brand points. Buy TEC. They are much more reliable and of much better quality. Your may be Daichi which is why they crapped out after 1 year.

If replacing the points/condensers fixes this issue, then move forward with a decision to replace the coils (5.0ohm units only) and the plug wires. If that is running well, then decide later about an electronic ignition. It can be added at any point, but its far easier to swap into a solid running bike and not as part of a diagnostic replacement.

[joeyrobots]

Calj737,

Thanks for the advice. I looked for the old condensers from when I replaced them last. The new ones were definitely Daichi, but I just replaced them because I read suggestions to do it occasionally as regular maintenance. The old ones were on there for 10 years prior. I guess if its not broke, don't fix it.

Despite your advice though, I went ahead and swapped out everything for Dyna parts. The coils were looking a little dodgy, I could tell they had been serviced before, and as I mentioned, the inner jacket on the plug wires for cylinder 3 was deteriorated to slime. Rather than go piecemeal through a system I knew was reaching the end of service life, I figured the least time expenditure and most peace of mind would come from a full swap. Its cold now, and being New York, i can't afford a garage so I have to do it all on the curb in front of my apartment with a headlamp. just wanted it done.

Replaced the ignition system in two hours. Adjusted the timing. Two kicks. Good as new!!!  Could be in my head, but i feel like its running better than before.

The main lesson from this is the one thing thats been on my mind for a while. Having my only bike down is very frustrating. I need another one for redundancy!

Also, i spent a while reading about your M-Unit project. very cool.

[calj737]

Good stuff, Joey! This no doubt that a healthy ignition system (points or electronic) will make a bike run much, much better.

Every bike owner needs 3 bikes, not 2. A sporty bike, a city bike, and a touring bike. A bleak and dreary winter is just the time to spend searching for your next project 

[Stev-o]

Every bike owner needs 3 bikes, not 2.

Only 3?  Guess I need to have a garage sale?!

[joeyrobots]

Oh yeah, I went out for a ride today and she revs up to the redline so smoothly, and a lot more power at high revs. I used to have a jumpy needle at idle but now it just holds 1500 nice and steady. And after a little WOT while I used to get spitting and popping, now its just ramps down evenly.

So happy.