Topic: 550 ignition problem

[Roodki]

I have a 74 CB550k, and it's not firing on the center two cylinders. 
I took the points cover off and checked the points, they look brand new.  I have about 5.5 volts at the point that is running the bike, cylinders 1 and 4, and about 4.2 at the one for the dead cylinders, if that means much.  I'm thinking maybe the ignition coil is bad. 

Anyone know how to test the ignition coil, or maybe steer me in the right direction for fixing this?

Thanks,
-Chris

[750goes]

check your power leads to the coils are nice and clean, and there is continuity from your points to the coils
can you check your resistance across the coils??
also make sure you have good contact between the plug leads and plug caps, if you have the screw in type you might be able to cut a little off the coil wires to get into some cleaner less corroded copper wire.

[OldSchool_IsCool]

First test to see if you have spark at #2 and/or #3 by connecting each plug wire to a spare spark plug.  Ground the plug to the engine case and crank the engine.  If you see a spark, it's not the coil or the 2.3 points.  If you have a spark, jump to "Got Spark"

Got No Spark: first check to make sure the 2.3 points fully open and fully close.  If they don't, set the gap of your points and static time them.  Search this site for procedures.  Check the yellow and blue wires between the coils and the points.  Check also the black wires that feed into the coils.

Still Got No Spark: To test the coil & points, swap #1 and #2 plug wires, #3 and #4 plug wires then swap yellow and blue wires at the point.  If 1&4 now fail to fire and 2&3 do, then it's somewhere in your coil, points, condenser or connection wires in between.

Got Spark:  May be a timing issue or something with your carbs/fuel.  Gap your points and static time them.  Sniff your #2&3 pipes for a gassy aroma.

[TwoTired]

With points open and ignition on, you should have 12v across the points and zero V when they are closed.  If the bike is running you will measure some average value in between, depending on the points gap setting.

There is a coil checking post in the FAQ.

http://www.sohc4.us/forums/index.php?topic=5752.msg8383#msg8383

Cheers,

[Roodki]

Alright...here's my story for today.

I took off the points cover and set the points gap to .014, like the manual said (.012-.016).  Tried to start her up and vroom, she purrs like a kitten.  Woo, all better.  I take it down the road , make it about 5 miles, then I approach a stoplight.  I come to a stop and then take off, and right then, bam, back down to 2 cylinders.  So I limp her back home, take the points cover off again, and I switched the yellow and blue wires around, then did the same with 1-4 wire and 2-3.  Start her up, and vroom, she's running like a champ.  Ok, so I switch the wires back to normal, put her back together and take her around the road.  This time I just went around the block a few times, to stay close.  Well, I probably road for about 10 minutes, and then bam, back down to 2 cylinders. 

It seems as if whenever I mess with the points, take them apart and put them back together it runs good again for a little bit.  Weeeird.  It almost seems as if something is breaking down from the heat, but it didn't really cool off much in the time I was messing with it to when I ran it again.

Any suggestions as to where to go from here?  I'll try checking the voltages

Thanks,
-Chris

[TwoTired]

Did you check to see if your spark plugs are fouling?

How about the wires that go from the points to the coils, Blue and Yellow.  What about the Black/White wire connections to the coils?

Cheers,

[Roodki]

The plugs are running pretty clean.  I'll check the wiring out tomorrow.  The thing is it doesn't have spark at the right side point, the one for cylinders 2-3.  I don't know if this is a good test or not...but when it's running on only cylinders 1-4 and I stick a grounded screwdriver near the 1-4 point, it'll spark.  When I do that to the 2-3 point nothing happens.  Correct me if I'm wrong because there's a very good chance of it, but that tells me that the problem is before the coil.

Thanks for the help.
-Chris

[TwoTired]

The sparking you see at the points is caused by the collapsing field generating power backwards in the primary.  The condensers are supposed to alleviate this somewhat and limit the heat causing the points to burn or melt.

All the lack of spark at the points tells you is that the coil isn't building and energy field.  No spark at plugs or points would be a jointly common symptom.

Make sure voltage is getting to the coils.  Then make sure that voltage can get through the coil primary and show up at the open points.

Wiggle wires around to see if can stimulate an intermittant connection/open.

Cheers,

[Kelvin8]

I had the same problem and tried all kinds of things to fix it. Installing Dyna Ignition and coils fixed it. Seriously, you can spend a lot of time and effort trying to get the OEM to work, but save yourself the wasted time and frustration.

[Roodki]

Woo, got her going strong again.  I just let it run on the 2 cylinders and started wiggling all the wires.  The yellow wire that connects to the coil was pulled out of it's connector.  So, I fixed that and she's good to go!

Thanks again for all your help.

-Chris