Motorcycle Repair: coil, emery cloth, plug caps

Question
how do you check a coil on a 450 honda motorcycle, with an ohm meter.
                             thanks

Answer
Joe, you didn't mention which version of Honda 450 you are working on.  CB450 1965-74 or CB450T from 1982-4 or maybe a CR450 MX machine. The difference in the readings relates to the type of ignition system used.

Points/condenser ignitions use coils with about 4 to 5 ohms or so. Electronic ignitions, including CDI are generally around 2-3 ohms. To check this primary winding resistance, you measure between the two small wire leads, the ones either from the battery or module and the one going to the points/condenser or pulser coil. If you have a twin, try comparing both coils to see if there are big variations in your readings.

Honda coils really don't fail very often, unless they are dropped, damaged from overvoltage or something like that.

If you don't have spark from a points/condenser ignition, clean the ignition points with a fine file or with emery cloth and then clean out any remaining filings or grit so you have clean, shiny and smooth surfaces on the point contacts. Set the points to open a maximum of about .014" as you turn the engine through a couple of revolutions, then move the backing plate to allow the points to just open at the F and LF marks. You can put a 12v test light or meter on the points and watch them switch on and off.
If you have everything clean and set correctly and there is erratic spark at the plug, then you may have a bad condenser or loose lead, which is shown by excessive arcing at the points. Check the spark plug caps, too, for resistance. Should be about 5k ohms from the plug wire end to the spark plug connector end.

Bill Silver