Motorcycle Repair: timing/points setup, maximum gap, emery paper

Question
hi bill, its carl again,the cb550 is up and running again, no leaks, but still popping in the exaust.i checked the timing again only to find it way off.my questions are,setting the points,where at? the f mark or when they are open the farthest?when the gap is set at the f mark i can get the timing on the marks using a stobe light,but its very hard to start.the clymer and the owners manual state at the widest point,but it is past the marks.set this way the baseplate is all the way to the right,it can go no farther,and the marks wont come even close to the marks.they are about a 1/2 inch to the right of them. same for the 2-3 points.the plate for them is all the way up.can the baseplate be taken off and moved to counter this? i have never taken them off.with the baseplat turned more to the left there is less popping from the exaust.any advise would be helpful.

Answer
Carl, ignition points are just switches to turn the ignition coils and and off. The point gap determines how long the coil primary windings can saturate the coil with a magnetic field. If the gap is smaller the points stay closed longer, which makes a larger magnetic field for the coil. Wider gaps mean that the points have to open earlier, thus reducing the coil saturation time. If the coil saturation is not long enough then the output will be lower and you get a high speed misfire. Points that don't open wide enough can overheat because they are working all the time drawing current through the circuit.
Honda has found that the proper maximum gap is .012-.014" measured at the WIDEST point on the point cam. This gap determines the coil saturation time... it is also called point dwell in automotive circuits.
The procedure is to clean the point faces thoroughly, so they are flat, clean and shiny w/o grinding a bunch of material from the point surfaces. Spray some contact cleaner on them after you have polished them up.. fine grade emery paper works fine or a point file will do the job. Once they are clean, you set the gap using a feeler gauge. Once the gap is set, then you can move the backing plate so that the points just open at the F mark. Points opening causes the magnetic field to collapse in the coil inducing a high voltage spike that travels out the plug wire to the spark plug.
If you are using the correct point gap and the base plate won't move enough to allow you to set the timing correctly, then there are two possibilities.
1. The spark advancer, located behind the point plate on the end of the crankshaft is stuck/sticking. Remove the point plate, and necessary hardware to access the spark advancer. Check it for advance and retard action. If it is stuck, remove the unit, mark the location of the point cam to the advancer base, spray some penetrating oil down the gap between the two parts and gently twist them until the free up, then lift the cam off the base unit, clean the shaft and the hole in the cam, lubricate lightly with point grease and then reassemble as before. Install point plate check point gap, move the plate to get points to open at the F mark and repeat with the other side.
2. In some cases, people install aftermarket replacement points are not correctly designed for the application and the geometry is not sufficient for the points to do their job in the same way the OEM point sets are designed. Replace the points with correct ND stamped points and you should be good to go...

Bill Silver