Posted by LenNH on April 16, 2008 at 16:36:08 from (65.96.146.183):
In Reply to: 10-20 start-up posted by bigr on April 13, 2008 at 18:36:46:
I have instructions on timing, but don't have time for a few days to go dig this out of storage. If I can help, e-mail me and I'll look for this next week. I'm a little confused about your confusion, but it looks as if you are not sure how the mag is "shut off." Both E-4A and F-4 mags have a grounding "switch" inside the lever that moves up and down at the back of the mag. When the lever is all the way up, the mag is supposed to be grounded, and any spark will go through the mag case instead of through the points and then to the coil. On the 10-20, the mag is supposed to be grounded when the "spark lever"--the front one of the two levers--is all the way to the left. If your mag sparks and you want to check to see if the grounding "switch" is working, make sure there is no fuel in the carb so then you can crank it over and have somebody hold a sparkplug wire near the block. If there is a spark, the grounding "switch" is not working. I haven't seen one of these in a while, but I think there are a couple of points that come together when the lever is all the way to the top. I suppose they could get corroded and not conduct current. These old tractors had "spark levers" because with kerosene, a very "low-octane fuel," knocking was common under heavy load. This was destructive to the pistons. If the driver heard knocking, he simply moved the spark lever (to the left in this case) until the knocking stopped. Of course, moving all the way to the left would kill the engine, but you didn't have to move much to stop the knocking. Cars up until the very early thirties, in some cases, had spark levers or spark knobs. The Ford A had a spark lever until 1931, and my father's '32 Chevrolet ton and a half truck had a knob like a choke that you pulled out to start, to avoid the possibility of breaking the Bendix drive on the starter (a kickback would break the drive spring, which meant dismantling the starter and installing a new spring). Retarding isn't a bad idea any time you are starting. The impulse coupling is supposed to retard enough so that the engine fires AFTER top dead center, but I got into the habit of retarding anyway. Still, I know I cranked sometimes with the lever at full advance, but being d.......d sure that the impulse was working. If you go over top dead center (you can feel the difference) and you haven't heard a click, STOP and check the impulse. On the E-4A, the impulse will stay engaged unless the engine fires a couple of times and speeds up the impulse enough to throw the lever out of engagement, so always take a look if you get a couple of pops but the engine does not continue to run. I made it a habit on our 10-20 to leave the hood up and to look at the impulse before I pulled up. Spinning, by the way, probably has very little value in creating a hot spark. The impulse coupling spins the mag, and if everything is working right, will start the engine after three or four pulls, if not before. My father had his arm broken by spinning a crank. Fortunately in one way, the 10-20 crank can't fly off and come up and hit you on the chin, but it can come backwards. If you pull up AND don't put your thumb around the crank, stand back enough so the crank can't hit you, you're safe. I guess I was a fuss-budget about cranking, because I never had an engine kick back. I HAVE seen it happen to other people, and I can tell you that an engine this big really packs a wallop. Each cylinder has about 70 cubic inches of displacement, which is nearly the size of the whole engine of some small European cars!
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