The front distributor was designed to come off of the tractor to replace/adjust the points. Remove the wire on the coil, remove the coil bail, remove the distributor cap & take the two bolts off. The base of the distributor has an offset tang & can only go back one way unless you really force it on.
6v or 12v? It could make a difference in troubleshooting.
Assuming that the points, condenser, bushings & advance weights are ok, the most common electrical failure (no spark, weak spark) points on the frontmount are:
1 The insulator under the concave head screw.
2 The insulator at the end of the points where the copper strip attaches.
3 The copper strip grounded to the plate.
4 The condenser wire grounding.
5 The pigtail/tab not making contact.
6 Incorrect positioning of the spring clip on the plate causing the pigtail to ground.
7 Incorrect seating of the coil on the distributor.
I’ll assume that if you have a 50+ year old tractor that you have a test meter.
First, confirm that you do indeed have a spark problem. Get the old plug & open the gap to 3/16”. Then, ground it to a rust & paint free spot on the engine, turn the key on & crank the engine. If the spark jumps the 3/16” gap, you probably don’t have a spark problem. If it won’t jump the 3/16” gap, you have a spark problem. There are ways to check for spark that work & ways that don't. Some folks think that checking for spark means pulling a plug wire off & looking for one. Well, it's the distance the spark jumps at the plug that gives you the info you want. It takes about 17kv to jump a 3/16" gap, so that's why you need to use a spark plug. Or, a store bought plug checker. There are other good ways to check for spark, but this ways work for me.
Next, turn the key on & crank the engine while you look at the ammeter. What is it doing? If it fluctuates, that means your points are opening & closing. If it shows a constant discharge, or doesn’t move at all, that means you need to do some more checking.
Next, check for voltage at the top of the coil. Battery voltage w/ the points open & about half of that when they are closed. If you do not have voltage to the coil, then move upstream to the resistor then to the ignition switch. As you check each component, wiggle it & the wires attached to it & watch you meter. Resistors break or get shorted & wires corrode.
If the voltage never drops when the engine is cranking, that means the points are not closing or you have lost contact between the pigtail & the brass screw or the tab & the cap.
Next, check for continuity inside the distributor w/ a meter. It is very easy to ground the tip of the condenser wire to the body of the distributor when you replaced the points. Also, make sure the condenser wire does not go through the same opening in the distributor that the coil pig tail does. The condenser wire goes the opening on the top right. Look at the points; are they burned, pitted or mis-aligned? Check the point gap, .015 on all four lobes. Make sure you have the star washers under the screws on the points.
Next, with the distributor still off the tractor, install the coil. Look at the pigtail on the coil; is it touching the brass screw w/ the concave head inside of the distributor? Don’t trust your eyes; test for continuity from the top of the coil to the points. If you do not have continuity, stretch the pigtail a bit until you do. (some people would rather put a small washer under the brass screw) Make sure that the pigtail is not grounded to the clip that holds the distributor plate in place; sometimes you can move the plate while setting the timing & actually ground the pigtail. Your meter should tell you this even if your eyes don’t! Also, look at the little tab opposite of the pigtail; bend it a bit also to insure that it will contact the distributor cap. Another common failure point is the insulator in the tab on the distributor plate where the brass screw w/ the concave head goes; it holds the copper strip from the points. Again, your meter will usually tell you if you have a problem, but you might have to wiggle the copper strip a bit. Once you are sure that you have good continuity inside the distributor, you should be good to go.
At this point, I just put the distributor, coil & cap all back on the tractor as a unit (it’s easier to do this from the left side). The reason I do this is because it is real easy to get the cap or coil mis-aligned trying to put it back together one piece at a time & the result is something gets broken or you get a ‘no spark’ problem.
Regarding timing, you do not need to find TDC on #1. You set the timing w/ the distributor off the tractor. Check out this link:
http://my9n.freeservers.com/tff/timing.htm
Regarding points.....the points open on the high point of the cam. The opening should be .015. As a newbie, use the .016 or .017 blade. (close counts) Make sure the blade is at a perfect right angle to the points & you want to feel just the slightest bit of drag when you pull the blade through the points. Make sure the blade is clean & that you dress the new points by running some card stock or a piece of brown paper bag through them.
Lastly, check out tip # 39 at the link below. A complete set of manuals will save you a lot of time & money.
50 Tips
