Got a problem that I can't solve...

72 ironhead was running ok until a couple days ago. Plugs started carboning up, back firing, sluggish, sputtering and basicly not running well...or at all.

Plugs are new, points are set at .018, checked coil and it specs out to what in book.....but the spark is very weak....almost none at all. 12 volts going to left side of coil, 2 volts going to points.

I did a check taking the plug wires, putting a wire in them and hold them 1/4 inch from motor while I separated the points with the ignition on. The spark was almost not seen....very week.

Anyone with any ideas?....would really appreciate it!
Thanks

 

my guess the coil is bad - you want 4.7 to 5.2 OHMs or the points will just burn up in short order -- dont know how you had checked the coil but its the only thing that creates spark and you dont have enough -- johnjzjz

 

thanks for your reply Johnjzjz.

I did check the specs with a meter on the coil and they seem to be in the range. (you can check the resistance between the 2 ends(primary) as well as both spark plug ports (secondary).)

I had an extra old coil sitting around and I put it in but the problem still is the same...but then I am not sure how good this coil was either.....both of them look to be 30-40 years old.....wonder what the life expecancy of coils are.....?????
Thanks

 

again its all a guess - not having it live to hear and first hand see whats its doing -

the points -- the condenser has become an issue not to over look - in the days of delco available replacements you could count the number of times one went bad with one finger, today the china crap even accel is china so dont trust any of it -- we see them junk new

if by chance you have an old delco condenser try it, i have seen just the condenser stop a bike dead along the lines of what you have, but having 2 coils go bad the same way NO thats not it -- jz

 

The "2 volts going to points" doesn't sound right. Are you sure it's not 0.2 volts? On my '69 with the points open, I get 12 volts on both small terminals of the coil. With the points closed, the voltage on the side of the coil going to the points drops to 0.13 volts.

I think you can disconnect the condensor completely and check the spark for a short period of time, but you don't want to run it for long like that or you'll burn your points up in a hurry.

 

Thanks Yellowstone Kelly,

I am corrected as is was .02 volts. I did a bench test today using a 12 volt battery charger connected to the left side(positive from the charger), putting a plug wire in and connecting the plug itself to the black ground from the charger to the plug. Then connecting a wire from the right side of the coil and touching the black charger clamp and releasing....expecting to see a spark on the plug....did not see anything.....it looks like the coil is dead....unless anyone else has a thought on this problem?
Thanks

 

A simple battery charger will put out only a few amps. It will not function like a battery in a test setup.

I should add that i do not understand the test that you did so i cannot comment on if it is a valid test or not.

These may be helpful in giving you a better understanding of the electrical system ...

Ironhead Charging System Checkout
http://xlforum.net/vbportal/forums/s...ad.php?t=39146

Ironhead Voltage Drop Testing
http://xlforum.net/vbportal/forums/s....php?t=1608465

 

Iron Man73, on my '69, I disconnected my coil from the bike's wiring and duplicated your bench test. I had one plug connected to the plug wire and coil, and the plug was out of the bike so I could see if it sparked or not.

I used a standard Sears 12 volt battery charger set to the 10 amp position. I connected the positive charger clamp to the + (input) small coil terminal, and the negative charger clamp to the metal hex part of the spark plug (this is the ground connection). Using another cable with clamps at each end, I clamped one end to the negative charger clamp/metal part of the plug (ground).

Each time I momentarily touched the other end of that cable to the - small terminal of the coil (replicating the points closing and opening), I got a nice blue spark at the plug.

So I think your test is valid, and either your coil, plug wire, or plug is bad.

 

Was there a spark at the wire you used to simulate the points? no spark as you place and remove, means no continuity through the coil. Best simulation of coil action is to take your coil and use your plugs and wires. use both plugs and tape the hexes together. attach a + battery charger alligator clip to one side of the primary and the - intermittently touch the other primary terminal. You should see both plugs spark, plus a spark at the - as you repeatedly touch the opposite primary terminal.

 

He has not said how many amps his battery charger puts out. 10 amps will duplicate the IronHead generator, but .75 or 1.5 amps of a normal small charger will most likely not be enough?