Tuesday, January 31, 2012

Motorcycle Woes

On a motorcycle, the usual battery is a 12 volt alternating current. 12 volts isn't sufficient, though, to create a spark that will ignite gas to cause a piston-moving explosion in the engine. The ignition coils of a motorcycle solve this problem by creating and collapsing a magnetic field many times a second and sending out bursts of much higher voltage along the circuitry to the spark plugs. To time these magnetic field creations and collapses along with the upward and downward motion of the pistons so as to get a high-voltage spark at the right instant, the circuitry is built into a rotating "crankshaft". As the crankshaft is turned by the pistons, the breaker points on the crankshaft connect and disconnect, alternately completing and opening the circuit connected to the ignition coils.

See picture of my breaker points below:

I noticed the other day, when trying to get my bike to start up properly, that the ignition coils were severely overheating. Taking off the cover to the crankshaft and rotating it several full rotations with a wrench, I realized that at no point during the crankshaft cycle were the breaker points actually opening. The circuit was never being opened! That meant the coils' magnetic fields were never collapsing, never creating the proper high voltage necessary to start and power the engine.

I adjusted the breaker points so that at their farthest apart they'd be .3 to .4 millimeters wide, the specs according to my manual. Then, according to the manual, I was supposed to do what's called a "continuity test" to make sure that the circuit was being broken at the proper time in the crankshaft cycle. The way you're supposed to do this is to ground one end of the tester to the engine, and attach the other wire of the tester to one side of the breaker point. The you turn the crankshaft until you see the meter needle drop, indicating that there is no power flowing through the circuit.

The needle never dropped! It looked like, even with the correct gap between the points, the circuit was ALWAYS complete. The magnetic field still shouldn't be collapsing! But after that first gap adjustment, the bike turned on just fine!

How was the bike turning on while the circuit was constantly complete? More importantly, why is the circuit constantly complete! Electricity isn't crossing that gap between the breaker points when they're open. It must be crossing straight across the base plate that holds the points in place. Some sort of insulation isn't working properly in the circuit, allowing electricity to flow where it shouldn't.

Here's a picture of the way the wires are connected to the breaker plates. It's a zoomed in version of the picture above, zooming in just to below and to the right of the central hex bolt:

So the electricity flows up the black and white wires onto the each of the two screws at the connections indicated by the red circles. It goes onto the thin spring breaker plate (visible on the left connection coming out to the left and heading up-left off the picture) and, theoretically, along the plate up to the point. It also, in parallel, goes into the condensers (the metal cylinders seen at the bottom of the picture). At the same time, though, it looks like the electricity is flowing onto the bracket that holds the screw in place, and down the bracket onto the large circular baseplate holding this whole contraption in place.

So that's the first problem! In summary, I can't do a continuity test to make sure the circuit's connecting and breaking at the right points of the crankshaft cycle because, according to my instrument, the connection is always being made, even when there is a visible gap between the breaker points with no spark crossing.

Remember, all of this is without the bike running. When I start the bike up (which it does easily), I see sparks arching across the breaker points. This isn't supposed to happen. The voltage should not be high enough for a spark to cross a gap in the air - it's damaging to the breaker points. With a spark crossing many times a minute, breaker points develop pitting over time that can destroy them.

That's the second problem.

The third problem is that whenever I rev the engine over around 2.5k revolutions per minute (rpm), the engine sputters out of and dies. We believe that this is due to a timing issue - as the crankshaft turns faster and faster, you want the spark to be exploding gas in the cylinders at a different point of the piston's motion. This probably has something to do with the breaker points as well, but we can't check the timing if we can't do a continuity test, which we can't do since we constantly have a closed circuit!

And those are all the issues with my bike right now!

Saturday, January 21, 2012

Sweet Bike Blog

If you want to spend hours looking at pics of classic and custom bikes, this is the place. Those Japanese Chopper clubs put our boys to shame!


Tuesday, January 17, 2012

I wrote up the following document to help Atticus work out some Gremlins in his Electrical system. Hopefully he will post his findings later.

The key is to isolate individual systems and test them, then components instead of thinking of the wiring loom as a whole.

Where to Start:

  1. First step, Look at your wiring diagram. See how many grounds you should have, and then go through and find them all, look for any others. There is no point trying to track down other issues until you know your grounds are good and clean.

    1. Clean them with scotch-brite or emery paper (300ish grit sandpaper) until the metal gleams on both the connection end and the frame/engine part.

    2. Re-attach with dielectric grease

    3. A lot of problems can be solved with nice clean grounds.

    4. If a connection is super corroded put a new eyelet on it.

    5. Completely replacing the main ground strap would not hurt.

  2. Check the voltage at the battery with the bike off.

  3. Check that your fuses aren't blown.

  4. Check your voltage to the fuse and what it is after the fuse.


  1. Understand your lighting system

  2. I would recommend sketching out something similar to this to simplify the wiring diagram so it is not cluttered with other stuff (lowbrow has a really cool example):

  3. Use a voltmeter to see what tabs on the back of the light are getting juice when it is set to high beam. If the voltage is different on high vs low then the problem may be with the bulb (burnt out filament or power plan (4)). If it does not change, move back to the switch.

  4. I know for my Yamaha Triple the headlight worked like this: One Ground, one hot for low beam and both hot for hi-beam. Once I traded out my bulb to a brighter one I had to change the wiring so that low was hot for hi but only the hot tab was hot for high beam. If the same thing happened for yours you should see if the high beam lights up if you only give the one tab a hot wire. See ill.

  1. See if you can check the wiring in the switch to see if the issue is the switch itself or if it is the wiring between the switch and the lamp.

  2. You can disassemble the switch (it is probably just a knife switch) if that is the problem.

  3. I would normally recommend starting from the battery and tracing the current at each component on its way to the switch but since we know you have juice at the headlight than we don't need to do that.


  1. Make sure you understand where the voltage goes to make your signal work.

  2. Make sure that flasher relay is getting voltage when the signal is turned. If it does not than make sure the switch is getting voltage. There are probably grounds at each of the turn signal stems (where they bolt on) clean and dielectric grease them.

  3. You can jump your bulb to see if the bulb itself works. B/c of the bi-metal switch in the relay if a bulb is burned out it will not have a circuit and the flasher relay will not heat up and therefore will not function.

  4. I had a bad relay on mine and when replaced it worked properly. My flasher relay was one out of a motorcycle graveyard but I have since discovered that you can just pick them up at AutoZone. You can tell which relay is the flasher relay by the wires that go into it (using your handy wiring diagram). You can jump the circuit with the relay out and see if your lights light up (a good test to see if you relay is bad). You could probably just do this step first but it will be good to do the other stuff to get to know where everything is).

How to attach a connection or repair a break.

  1. You can do a better job with a soldering iron but since I do not have one I usually go without. Trim back enough wire insulation to show the copper inside (usually about ½”).

  2. Slip an appropriate length of shrink wrap over wire (make sure it will fit over the connector when crimped).

  3. Cover wire in solder, insert into connector, and crimp. I use hefty channel-locks to make sure it is well crimped.

  4. Slip heat-shrink over connection, and heat with lighter or hair dryer.

  5. For wire to wire connections you can solder them together w/o the butt-connector and then heat-shrink but again, I use butt-connectors b/c I don't have a soldering iron.

Monday, January 9, 2012

1978 Suzuki GS550

Want to learn how carburetors work? Just found a site all about them. It might just be able to help out with getting my bike to idle properly. We'll see! I'll be heading over to work on the bike tomorrow, and will be posting some pictures of it after I've got my new air filters on it!