1937 rd4 magneto w/o spark

Run a point file across the points in the mag. Look at the spark, if it is yellow, change the condenser.

thanks Soapy,,, How do you get into the mag? It looks like a little motor on top at the rear of the engine right above the pony motor, I'm a bit concerned that if I take it off the motor then how does one get the timing right ? Thanks Doug Horvath

You should be able to remove the cap and check it out first. You might need to remove a few things that are in the way.

You have to take the throttle linkage loose at the carb, in order to remove the cap. Should be a screw at each corner of the cap. If is is like my D-2, there is a removable access cover on the firewall, to enable you to get the screws out. If not, there is a 3/8 pipe plug on the housing the mag bolts too, plug is toward the main engine. To retime, remove the plug, and line up the marks on the drive gear, and the driven gear on the mag, that are visible through the plug hole.

don't remove the mag unless you have to, if it was running last year and no spark this spring it probably just needs the points cleaned and regapped. i know the d4 and d2 mags are not fun to access and work on.

if you do end up removing the mag, time it before you remove it. makes re-installation that much easier. clean the points with a points file, if you can find one, i have tried at all my local parts stores and industrial supplies and every one looks at me like i am from another planet.

pop the cover off the mag, remove the rotor, use a small pick or screwdriver to open the points, file the points so they are nice and clean. a nail file/emery board will work if you don't have a proper points file. mke sure all dust and corrosion is removed. i usually just blow on it really hard, i don't know what the spec is for your mag, but it will usually run if the points are set between 0.012" to about 0.018" if you don't have feeler gauges for setting the points, use a cigarette pack or a matchbook cover, even a cereal or cracker box will get you close enough. the points are set at maximum open so you need to rotate the engine until the points are at the widest gap when you set them. there is a small adjustment screw and there is usually a slot for a flat screwdriver to tweak the point adjustment after snugging the adjuster screw.

clean the rotor poles up a bit and the electrodes inside the cap. put it all back together and it should run.