Burned points

rrwayside · Post by **rrwayside** » Sat Jul 28, 2012 8:19 pm

Put in a new set of points this morning ,gapped them at .022.It ran good for a half an hour or so,then started skipping.Checked points and the were already burnt somewhat.Should there be some kind of resistor or something and if so where in the wiring should it be located?

shinnery · Post by **shinnery** » Sat Jul 28, 2012 9:48 pm

If you are running a 12v ign circuit and the coil is not marked for 12V use and no resister needed, you probably should put one in. Normally they are installed in the 12V lead from the switch to the coil. One purpose of the condenser is to reduce point arcing and burning, you may want to be sure it is the right size and functioning.
Bryce

whiteclipse16 · Post by **whiteclipse16** » Sun Jul 29, 2012 6:59 am

Like skinnery said, check the coil voltage. I think on some the resistor is built into the key switch. If you just measure voltage at the coil when the key is on the run position that will tell you if there is a resistor somewhere in the wiring. You should do it this way so that you give three coil 12 volts only during starting to get a better spark and make it start easier.
There will always be some burn on the points. If there is an arc there will be burn.

Scottyb · Post by **Scottyb** » Sun Jul 29, 2012 9:31 am

I was burning points out of my garden tractor every 10 hours or less of running time and was at a loss to figure it out. Then my neighbour told me I had the wrong kind of coil and that I should get the built in resistor type. The tractor had a resistor on it (new) and still does. I bought the one he recommended the next day and it has run perfect for the last year without any issue.
I can't explain it but it fixed my problem.
Hopefully someone here can explain the difference in coil types.
Scott

LarryD · Post by **LarryD** » Sun Jul 29, 2012 10:10 pm

If it was running ok before and nothing else changed other than points, best bet is you got a bad condenser. The condenser absorbs the " coil ring" that causes the points to arc. Bad condenser.......arcing points.

Larry

Paul Buhler · Post by **Paul Buhler** » Mon Jul 30, 2012 7:27 am

Just a thought, check that you have a good, solid condenser mounting. I had one that had intermittent grounding that caused me problems in my 420until I found it (6v, positive ground system). Paul

rrwayside · Post by **rrwayside** » Mon Jul 30, 2012 7:10 pm

Thanks again to everyone.I checked the coil,it said no resistor required.I changed the condenser yesterday and it has been running good every since.BUT stay tuned for the next problem.

Scottyb · Post by **Scottyb** » Mon Jul 30, 2012 9:00 pm

I know your relief, electrical problems are such a hassle. Good to hear you got it going

your question got me looking at coils however and I learned a few things.

Some engines wont start when cranking but as soon as you release the starter they fire up. I have had this problem with gas engines.. It is because of the voltage drop at the coil when cranking. There is solutions for this on the net. The same solution might help gas crawlers start better.???

Other use for resistors...,
I found this..
" Do I have to use the 12 volt coil? There is nothing wrong with my 6 volt coil and I prefer the original."
A. No. As with most automobiles manufactured in the late 50s and 60s, picking up a cheap resistor at the auto parts store will allow you to use the 6 volt coil.

Maby I should move this over to Off topic discussions??
Scott

Scottyb · Post by **Scottyb** » Mon Jul 30, 2012 9:39 pm

I think I found out why I was burning the points off in MY tractor before I changed the coil....

Found on the web.....

Here"s the deal. If you have an old tractor with 12 V system, you need to have a total resistance in the primary circuit of 3.2 ohms to limit the point current to around 4amps max. If you check the cold resistance of the coil and it"s 1.6 ohms (I call this a 6 v coil because it can be installed in the 6 v system with no additional resistance), you need to add a resisitor of 1.6 ohms in series to limit the current in a 12V system.
If you have a coil with 3.2 ohms resistance( I call this a real 12V coil) then you just need to install it. No additional resistance is required in a 12V circuit.

Hope this helps someone somewhere...
Scott

LeonardL · Post by **LeonardL** » Thu Aug 02, 2012 7:54 am

Hey Scott,
Just curious what machine this is on?

Scottyb · Post by **Scottyb** » Thu Aug 02, 2012 8:41 am

Leonard, My point burning problem was on my Case 444. When I got it from my Father in law he had recently put a new coil on it. I turned out to be the wrong one.
I thought rrwyside had a similar sounding issue.
The other quotes that I posted, were found when I goggled burned points and coils. They were not specific to JD crawlers, but with so much after market repairs happening I hoped the info would relevant.

LeonardL · Post by **LeonardL** » Thu Aug 02, 2012 12:21 pm

Okay, I was just curious if it was a Deere machine or something else. The Deere gas burners had a resistor behind the dash panel that would go bad and cause what you were describing. I haven't been around much of the Case machines other than the old Case C/Ks. A few of the later model farm tractors from the old 990s on up. Most of them were just David Browns with Cases name on them.
Sounds like you got your problem going so I will leave it at that. Take care!

Scottyb · Post by **Scottyb** » Thu Aug 02, 2012 1:24 pm

Thanks Leonard. I have had this point burn out issue over the years including recently on my late 70's honda Goldwing and this thread got me thinking that It is time I figured the whole thing out rather than the old approach I had used...Just keep changeing parts until it works! I also have had a few gas engines that would only start after the starter was released ( my old suzuki CJ for one ) and I found out that all these issues are related to resistors and the coils. Condensers are important too!.
By the way very funny recount of the friend using a tree to lift his loader, I always enjoy a humours story when no one gets hurt!
Scott

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