Topic: 1976 CB550K: Bad coil? UPDATE

[Nortstudio]

Stock coils, new plug wires (with NGK splicers) and caps.  Hondaman ignition.

I just got home from a 1288 mile trip from Brooklyn down through the Skyline Drive of the Blue Ridge Parkway and back.  The bike ran pretty amazing the whole trip, including a flat-out 'tuck-n-twist' ride for the last two days home, at about 75-80mph.  Went to fire it up today for the first time since getting home, and it sounded weird.... 

Checked the pipes, and 2/3 were cold to the touch.  I do not have a multimeter here at home at the moment - so I first checked to make sure there was gas in the float of those carbs - there was.  Checked the spark plug boots to make sure they were snug - they were.  Looked at the plugs themselves, and they had a hair of moisture to them and smelled of gas.  I checked that the black/white wires were plugged in tight to the coils - they were.

It was running on the 2 cylinders, but would die when I let off the throttle, but just to check, I swapped the boots from 1/4 to the  2/3 plugs (the other wires won't fit over to the wrong plugs) and it backfired like I have never heard before.  I swear, a dude walking on the street actually screamed

I ended that test immediately....  Unfortunately most of my tools are at the garage, but I'd love to know what to check when I get there.

Assuming it's a bad coil.  Sound about right?

Thanks folks!

Scott

It seems that the

[Gordon]

When you swap the plug wires you also have to swap the blue and yellow wires on the coils or you'll get the results you got. 

Coils rarely go bad, so I wouldn't make them the main suspect right now.  The dead cylinders being 2/3 could mean it's an ignition problem, but it doesn't have to be.  The spark plugs may have just gotten gas fouled and won't spark until you clean/dry them off.  If it's ignition related, could be a bad condenser or a wiring issue on the points. 

[Nortstudio]

Thanks Gordon. I definitely didn't swap the wires, so I guess that test was moot. I will swap out some good plugs to check if they were just fouled. I wiped them on my pants - but didn't clean them thoroughly.

Is there a simple way to test the condenser?  Should it show a measurement from one end to the other, with a multimeter?  I'll check the wires in there too when I get the points cover off.

Appreciate the response.

[OldSchool_IsCool]

The Hondaman module kinda renders the condensers moot too, but you could switch the two condensers to the opposite points set to see if the fault follows or stays put.  You may also want to connect the points to the coils direct (take out the HMM) for a test.  You mentioned moisture.  Realize that with the HMM, you now have a small trickle of current flowing thru the points.  It doesn't take much craption on the points faces to block that wee bit of current.

And yes, if you switch the 1.4 plug wires to 2.3, you also need to switch the blue & yellow wires too.  You can do that under the tank or at the side by the rear brake switch if you don't have tools to take the points cover off.

[Nortstudio]

I'll give these tests a try tomorrow - had to run.  I appreciate the clarification on the HM ignition.  I'll swap the blue/yellow and caps first and then see if I have to take the the HM out all together for more tests. New plugs when I get to the garage too.

So weird it happens right after I had such a successful trip - but I guess I will look at the upside, it could have happened on the road!   It ran perfectly right up to my door.

[mjstone]

If you can get to your points, look them over real good.  I had the phenolic rubbing block ( the part of the points that rides on the cam) break off on my 2,3 points twice.  If it does the points will not open and you will not have spark on your 2,3 cylinders.  This is why I went with the Pamco ignition over the Hondaman that I was originally going to get.

MJ

[Nortstudio]

Thanks MJ.  I will check that out for sure.  Those little things always do look a little brittle.

[Danno]

if you grease the cam the block rides on that rarely happens also these bikes are known for sometimes having the points cam out of square with the ignition plate which will grind the block off the points

[Nortstudio]

I swapped the yellow and blue wires at the points (bullets near brake switch) and the plug boots again, and it fired on #2/3 just like it has been on 1/4. So it seems that test is done.

I swapped the condensers, and still 1/4 fired fine - but no 2/3. I did this as a seperate test. SHOULD I HAVE DONE THIS WITH THE BLUE & YELLOW  WIRES AND PLUG BOOTS SWAPPED AT THE SAME TIME???

Cleaned out the points with a business card. Still no luck. Checked to make sure the block is there on points 2/3 and it seems fine. The points both seem to be operating fine (to te naked eye - they open and close as they should).

To remove the HM ignition, do I need to remove the black wires running up to the coils, or can I just jump the blue & yellow back to the harness going to the points?

Thanks for all the help folks.

[OldSchool_IsCool]

OK, that test shows that the carbs, mix & plugs are fine.  Looks like an issue with the 2.3 coil, points or wiring.

To remove the HMM, just connect the original blue coil wire to the original blue points wire.  Same for the yellow.  Plug wires back to their original plugs too.

Next test.  Key on, kill switch on, bike not running.  With a multimeter on the 20v setting or with a test lamp, do you get 12v between the blue wire and ground when you hold the 1.4 point set open with your fingers?  Same for the yellow? 

[Nortstudio]

Thanks Old School.  I will test this as soon as I grab my Multimeter.  When you say test the blue and yellow wire, so you mean at the points, or at the bullet connector before it makes the run to the points?

[OldSchool_IsCool]

It's prolly easier to test them at the points where you can clip your multimeter to the blue or yellow lead and to ground then manipulate the points.

[Nortstudio]

Thanks.

[scottly]

Also, with the points closed, you should read 0 volts.

[Nortstudio]

Shot off an email to Hondaman about the transitorized ignition.  Like you, he suggested I swap out the unit back tot he points directly, and the minute I did, she fired up on all 4 cylinders.  Seems he got a bad batch of resistors somewhere along the way - so I need to get this unit back to him for him to swap in a new one.

Thanks for all the help folks.  Looks like I can run it as is - until I receive the repaired unit.

Nice to still have points on the bike in this situation I guess.

Scott

[Gordon]

Glad you got it figured out.

[OldSchool_IsCool]

Good Deal!