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a little tune-up idea for all tractors
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Posted by RKS on May 21, 1999 at 20:09:05 from (171.212.107.223):
Are you tired of having cranking, running, or charging problems? They may all be related and it is very common on these boards to see these problems creep up. Much grief might be eliminated by owners if they would just perform a top-notch tune-up on the ignition system and/or carburetor, depending on how the tractor cranks and runs. It will make the electrical system appear to work better, and make the tractor more efficient to boot. Too, cranking problems that used to be blamed on the carburetor might just disappear. You 6V people really need all you can do to improve cranking and running, huh? Here is one idea I hope you appreciate. I think it makes good sense, and I've had good luck with it on automobiles and tractors alike. Why not consider advancing the timing on your engine just slightly the next time you tune it up. Think about it. Is that tractor running the same type fuel it used when new and for much of its life afterward? The answer is no - - that fuel isn't available now regularly. Say thanks to the EPA for that. Fuel doesn't burn as evenly or detonate as rapidly, regardless of grade, as it used to when tetra-ethyl-lead was used, and you usually can't get the high octane gasoline that was available and common then, unless you have a line on aviation gas, or avgas. Anyway, do you realize how "slow" the detonation within a piston engine is, particularly when that engine was designed for fuel with a much faster rate of detonation, and lead was added? At just 450 rpm, a speed that most engines almost stumble at, the flywheel is moving through 7 1/2 revolutions per second, or about 2,700 degrees of arc - - each second! Consider for a moment how long it takes the flywheel to rotate through just 2 degrees of arc. It works out to .00074 seconds, or a little more than 7.5/10,000's of one second. How long do you think the gasoline detonation inside the cylinder takes? Remember that the timing is supposed to also be checked for advance at higher rpm, such as 1,200 or 2,000 rpm and that those advances are supposed to be something like 20-45 degrees, or more!! Does that give you an idea of how really slow it can be? I like to watch car racing, and I remember watching the first time trials in which cars qualified at 200 mph. Know how far a car travels at 200 mph in .00074 seconds? (hint: 60 mph is about 88 ft/sec) **About 2.6 inches!** (near the width of the average man's wrist) - - and in about the same amount of time that 2 degrees of ignition timing advance takes at only 450 rpm. Want that old tractor to run like a sewing machine, and give the battery and starter a little help? My old 1941 Farmall "H" cranks when I whistle. In fact, I think it likes to crank,- - sometimes I have found it running from "spontaneous cranking" ha! - - and I think it has something to do with advancing the timing just a tad. Why don't you try it? Put the timing light on your engine, set it to factory specs, and then try advancing the timing just a tad, say about 1-3 degrees at 450-500 rpm from what the mfg recommended. Don't advance it enough to lug down the engine. As you advance, it should smooth out and quiet slightly, with a slight increase in rpm. You can find the right setting by listening and/or watching your tachometer. You see, you'll be correcting the timing slightly to take into consideration the slight delay in detonation of the lower quality fuels we have today. You'll be placing the "expansion" of hot gases, which happens later in the detonation, closer to where the mfg designed it to be (that is - - nearer to the old recommended timing mark). The engine should crank and run better, be slightly more efficient, and even cool more efficiently. Give it a try. RKS
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