Motorcycle Repair: Ignition Question, honda xr 80, nuts and bolts

Question
I recently obtained a 1983 Honda XR 80 from a friend.  It's been sitting awhile, so I cleaned out the carb and checked for gas.  The tank was rusty.  I put some nuts and bolts in the tank, shook her up, replaced the gas a few times.  Put a filter on too!It's getting gas in the carb.  I checked for spark. No spark.  I bought new spark plugs.  No spark. I put a steel nail in the spark plug cap and was getting spark.  I figured the problem was the coil, because the points looked fine (no rust)and the bike was hardly ridden.  I bought a new coil.  No spark.  Help>>>John Krajovan

Answer
John, the ignition system is a basic magneto with magnets passing some small coils inside the stator/flywheel combo.

Getting good spark does require very clean points. They generally don't rust but can get a thin film of corrosion over them, that keeps them from doing their job. If the points are clean, then the next culprit could be a weak condenser, which are usually soldered in place. After that, I would check the insides of the flywheel for rust in the magnet section. You will need the correct flywheel puller tool to get it off. Don't use gear pullers or other non-specific tools to remove the flywheel or you will damage something.

Point signal comes up from the magneto, heads to the coil, of course. Check the resistance in the plug cap first. Resistor caps are usually about 5k ohms. More than that, replace it. Remember that steel nails have no resistance, whereas a spark plug has a gap to jump before it can make the spark connect to ground, and sometimes there are resistors inside the plugs, too.

Don't overlook the kill switch. Sometimes the contacts inside get corroded from sitting and can bridge across, killing the spark.

Honda coils are pretty reliable. They sell a lot of them to people who don't do their basic troubleshooting first!
:>)

Bill Silver