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JD M 12 volt conversion

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Mike Revelle

12-12-2002 12:47:49




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I recently purchased 2 JD model M's. One was in pretty rough shape and the other nearly original. I plan on restoring the original one back to"showroom condition" but I've always wanted a little M to keep around for small chores around the farm. Oddly enough the "original" tractor had been converted to 12v and the rougher tractor remained a 6 volt system. I have put a 420 type 3pt hitch on the rougher M and decided to convert it to a 12v system so that it could run modern 12v lights and in case I needed to boost off the tractor I could do it with equipment that I already have. None-the less, since converting the M to 12 volt I have had horrible problems with plug fouling!! I replaced the coil with a 12v, changed to negative ground and added a Delco "one wire" alternator. The alternator charges great(after reversing the wires an the ammeter guage) and when fresh plugs (I've tried Champion H8, H10, and H12) are added the tractor runs great for about 3-4 hrs then the plugs are fouled. The tractor doesn't smoke or use any oil as far as I can tell. At first I didn't put the resistor in the circuit and was told this might be my problem but I have since changed that but it still fouls the plugs. I've even tried the "splitfire" plugs,.... not any better!! Reading the manual tells me either I'm using the wrong range heat plug or the piston rings are worn. I didn't seem to have this problem when the tractor was 6 volt (which is a strong argument to convert it back!) however, I would like to leave it a 12 volt. Any Ideas on what I'm doing wrong or how to remedy this situation?

Thanks!
Mike

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bob

12-13-2002 01:58:01




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 Re: JD M 12 volt conversion in reply to Mike Revelle, 12-12-2002 12:47:49  
a simple machine needs simple tools and there is always a simple answer to fix the problem.....



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Clooney

12-12-2002 14:47:46




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 Re: JD M 12 volt conversion in reply to Mike Revelle, 12-12-2002 12:47:49  
Mike, monitor the coil voltage at the distributor side. You want it around 6-7 volts running at fast idle. If lower, remove the ballast resistor or try switching back to the 6 volt coil with the resistor. Not all 12 volt coils are made to run at 12 volts [some are meant to use a ballast resistor & others are internally resisted]. The best way to get your system right is to measure the running distributor side voltage.
~The ignition switches are prone to problems in the M & internal resistance is a possibility [try powering the coil directly from the big post on the starter for a few days to see if the problem improves]
~If you are going to keep & use that 12 volt coil install a Delco D-203 condenser [the stock 6 volt condenser is not matched to your new coil.
~Check the ignition wires for solid metal core & if carbon core TVRS wires are on it replace them with solid core wires.
~Go to H-12 plugs at .025"-.030" & use 2 gaskets under each plug. [the M seems to like a slightly smaller plug gap]
~If after checking all the above you are still fouling plugs suspect a ring or carb problem or even a partially plugged air cleaner.
~If you are using premium fuel, fuel additives, old fuel, or summer fuel, try new fresh fuel.

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John T

12-12-2002 15:51:03




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 Re: Re: JD M 12 volt conversion in reply to Clooney, 12-12-2002 14:47:46  
Clooney, what type of voltmeter do you recommend for a distributor (to ground) side running coil voltage measurement?? When the points are closed (more often than open) that point (low side of coil) is dead to ground (o volts) via and through the points, and when the points open and condensor is charged up, if no current is drawn, it should be near battery voltage. While an "ideal" voltmeter is infinite resistance, depending on the RPM and the current draw of different types of voltmeters, that voltage figure on the distributor side could read different. An expensive voltmeter, of course, isnt going to draw as much current as an el cheapo. I still enjoy usign my old Simpson 260 analog with a real needle I can see deflect, but the newer digital types are probably more accurate and might yield different results on such type measurements. Keep warm and dry up North there. John T

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Clooney

12-12-2002 17:05:54




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 Re: Re: Re: JD M 12 volt conversion in reply to John T, 12-12-2002 15:51:03  
John, you have a point there. I use a good digital Fluke & it is very low impedance that has a good averaging ability. Even my old Snap-On analog is dampened. I do have an old cheapie simple un-dampened analog & next time I measure a coil system I will see how they compare....



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John T

12-12-2002 20:54:25




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 Re: Re: Re: Re: JD M 12 volt conversion in reply to Clooney, 12-12-2002 17:05:54  
We used to some very expensive electrostatic types at work for use in low voltage energy situations where most voltmeters would draw down the voltage so much you couldnt get an accurate reading, and thats why I was wondering how the duty cycle of the points due to RPM, the capacitative action of the condensor charging up and discharging, plus the averaging capability and type of meter could sure change things at the low side of the coil. In my seminars for easy simple troubleshooting, I just tell them a test lamp there should go on and off (points have that connection dead grounded when closed) as the engine is cranked slowly, becauase if it doesnt go off, the points arent closing or are corroded etc. John T

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bob

12-12-2002 14:02:09




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 Re: JD M 12 volt conversion in reply to Mike Revelle, 12-12-2002 12:47:49  
and make sure you have a resistor..ceramic



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Lowell

12-12-2002 14:47:33




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 Re: Re: JD M 12 volt conversion in reply to bob, 12-12-2002 14:02:09  
is your coil stilled wired like it was when it was 6v pos. ground ? if so you need to cross the primary wires to the coil. your sprark may actually be jumping the opposite direction which can cause your fouling problems hope that helps.



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bob

12-12-2002 13:59:06




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 Re: JD M 12 volt conversion in reply to Mike Revelle, 12-12-2002 12:47:49  
use a 6 volt coil.



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John T

12-12-2002 13:13:02




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 Re: JD M 12 volt conversion in reply to Mike Revelle, 12-12-2002 12:47:49  
MIke, it seems not too long ago there was a long discussion of M's and their tendency to foul plugs so you might scroll back a few weeks and see what was posted then. If the new coil you purchased is a 12 volt as you say, they are often internally ballasted, in which case you dont want or need that external ballast. The purpose of the internally ballasted 12 volt coil is to limit the currrent flowing through the points to 3 to 4 amps to promote their longevity and also limit the coils current and resultant heat. Its already designed for 12 volts and adding anymore ballast will result in it running at too low voltage and a weaker spark, so remove it and see how it works out. Next, when the plugs foul, are they a flat black sooty color (excess unburned fuel) or a wet shiny uneven black color (excess unburned oil)??? Fouling can be due to not a hot enough running plug or excess fuel or oil or a weak spark. Does it have wire core and NOT carbon core suppressor type automotive wires??? Use wire ones. Is the cap and rotor clean and free of carbon tracks or cracks??? Is the air cleaner clogged, or is the choke butterfly not actually opening wide???? That would cause premature gas fouling but the exhaust would be a little black looking probably. A suggestion is to insure the air intake is clean and choke opening, run the HOTTEST plugs you can buy, gap them at 0.035 or even try 0.040, add another washer at the plug, clean and re gap or install new points and condensor, lean the carb a bit and see what happens and all this with that ballast removed. Let us know Ol John T Nordhoff in Indiana

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