09 December, 2010


How many tools does it take to troubleshoot no spark? Please to see below:

So, hear is the long story.

This model of Bridgestone uses a magneto ignition. It has a separate ignition coil and a separate lighting coil. For now, all I care about is ignition, as I likely won't run a headlight on it. Luckily, all of the Bridgestone service manuals are available online, including wiring diagrams. The diagram for the ignition circuit is very simple. Black wire from stator through a switch, and then to the black wire on the coil. Green/white wire from stator to green/white wire on coil. Coil is grounded to chassis through its mount.

I had no spark.

I took off the stator and gave everything a thorough cleaning. Removed a lot of rust from the flywheel, lubed the felt pad, and ran some emery through the points.

No spark.

I then decided to eliminate the stock setup and wire it up as a battery ignition, using a 12v battery and a 12v coil. This is very clearly shown in the factory Bridgestone Race manual, which is also online. So I did that, thinking maybe the stock coil was bad.

No spark.

All of this took place over the past few evenings. Today at lunch I came across an excellent tech tip on the Bridgestone forums. It discussed the full operation of points, and how even the slightest amount of oil on the points could make them not work. I realized I may have been too liberal with my penetrating oil when I was cleaning and lubing, so tonight after work I hit the points with electrical contact cleaner. I also ran a strip of paper that was soaked in acetone through the points to clean them.

I instantly had a fat spark. This was with it wired up in the 12v battery setup. I switched it back to stock wiring, and put the flywheel back on. Same fat spark!

Just to make sure I didn't do anything else to solve this, I ran an old piece of oily paper through the points. No spark at all. After contact cleaner and the acetone trick, big fat spark.

So, long story short, I had dirty/oily points.

Next step is to clean out the gas tank and run a fuel line and fuel filter to the carb. After that, I may be ready to try and start it.

Oh, but first I need to set the timing. I'll do that tomorrow night.


1 comment:

sean said...

Awesome! It's seemingly always the simple shit.