Weak Spark

[Randytheorgfarmer]

This is my sons JD 40C, 5 roller with a 62 blade. He saw it at the local scrap yard and had to have it, a basket case for sure. He paid $1000.00 and we have been buying castings from Lavoy, nickel and diming us for about five years.
Well today was the day to try to start it! Thought for sure we could make it run. A little background, we didn't know if it ran, changed the oil and filter, put on new 12 volt battery, did compression check(good), new plugs, points and condenser rotor cap wires. The rotor turns, number 2 plug has a good orange spark, number one has a very weak to no spark. Took both plugs out to see the spark on the engine as a ground, number one jumped nearly an inch! and steady rhythm. Number two not steady rhythm very weak to not at all. We tried the wire and plug from no. 1 but didn't make any difference. The cap is a good new cap brass not the new cheap aluminum. We changed out the condenser three times. Checked the new cap for continuity making sure the brass is not bad from the factory. Oh yes it does turn over well but does not fire even with a little ether. Any one seen anything like this? Any ideas?

Randy

[Stan Disbrow]

Hi,

Sounds like the alignment of the rotor to the cap is off for the second cylinder. That would make the most sense.

It also bothers me that the spark is orange in color and not a much hotter blue. Yet, it sparks a long way. Those wires are actually wire, right? As in copper. Not carbon impregnated fiberglass strands. They can cause orange sparks.

There is one oddball thing I have seen before, though. It is supposed to be 6v to the coil. Is there a ballast resistor between the battery and the coil? If not, then maybe the magnetic field in coil from the first impulse is bucking for the second impulse. At 12v it would be way stronger than it ought to be. It might not fully collapse before the next tries to generate. But, I have only seen this happen at higher RPMs....but thought I would toss it out there anyway.

Stan

[Randytheorgfarmer]

Thanks for the reply,

I first must make a correction my son said we have a 61 blade.

We did put on a new coil today no change. We do have copper wires. I thought about rotor alignment, checked it out everything good? We think the cap is bad but we don't have an old one to try so have to wait til after the holiday till the part comes in. We had a farmall 504 with a bad new cap this summer but it was an aluminum one, this one is new brass from TSC I think it is bad, guess we will see.

Thanks Again,

Randy

[gregjo1948]

Being an orange spark on #1 and little to none on #2, I would try changing the coil.

[Randytheorgfarmer]

We have it running, it helps to put the correct cap on, the cap must have been from another engine, it was 90 degrees off. Put the new one on it started instantly. Thanks for all your help.

We drove it up and down the drive way, the steering clutches are slipping. so if the steel plates are rusty the fiber plates are worn to about .130 to .135 thousands which is less than the book calls for at about .140 to .147 thousands
is this why it is slipping? If so why can't we just adjust up the presure plate bolt to extend the operating range of the pressure plate??

Randy

[Stan Disbrow]

Hi,

Oh, dear. Or, should that be Oh, Deere??

Being the wrong cap would certainly alter the timing!

The funny thing about pressure plates is they lose spring tension as the stack height drops. So, there comes a point where they will slip regardless of adjustment.

Stan

[Lavoy]

Depending on the pressure plate at some point you run out of travel on the plate itself. So it comes down to if it is worth it to you to save $140 and keep pulling the final when it doesn't work any more.
Lavoy