300 burns up points

VaGasman

New User
I had posted this several months ago and
thought I had it cleared. But My RC 300 is
burning up points. In late summer if I let it sit for
2-3 weeks ,I would try to start and no fire.
Check points and file them and it would fire
right up. This occured every 2 weeks if I did
not keep it up and going. Then I replaced
points and condensor 4 weeks ago and it was
good until today after Church I tried to start
it and no fire . Checked points and they are
burned. Filed points and it takes right off to
sit out a bale of Hay. At the beginning of hay
season I replaced coil with 12v from advance. a
universal coil. this has been a 12v since I
have had it the last 2 years.
What should I look for???
Thanks, Randy
 
Check for voltage cross the points with the key off. If that's not the problem, try adding a second condenser. That solved the problem on my H.

Greg
 
I have a farmall H that acted the same when I first got it. After it was running and then sat a few days, I would have to re gap the points to get it running again. It had a couple problems, it was converted to 12 volts and the resistor was hooked up wrong.when it finally refused to run at all, I discovered that the distributor wasn't turning. The pin holding the gear in place on the shaft had sheared because the hole in the shaft and gear was wallowed out. It has a verticle mount dist. because a live hydraulic pump had been installed.
 
"Universal coil" doesn't tell us much.

ASSUMING it is a coil for use on a 12 Volt system WITHOUT needing a primary circuit ballast resistor, HOPEFULLY, the coil is not the issue.

If that is the case, poor quality breaker points likely are issue.

Plus, once you have filed points, they are JUNK, only good enough to get the tractor back to the yard, for convenient point replacement.

I will get flamed for that comment, but it is true, most of the time.

If you want to argue, look at the smooth, shiny face of quality new points, then take a look at a set that has been filed/hacked/tore up/ruined.
 
You have to determine if your coil requires a external resistor or not. Simple ohm meter test of primary winding will tell you that. Less than two ohms, you need resistor. Approx 4 ohms, it is a straight 12volt coil and does not need resistor. Most coils used on 12 volt systems DO require a external resistor. Many other ways to check this also but this is about as simple as I can state it.
 
Of course, he could always look up the part #, manufacturer's data/"specs" for the coil.

Not much drama involved in that, though.

And not many tools needed for that, either, which, of course, flies in that face of the man motto "the more tools, the better"!
 
I had same issues with tune up kit from Tractor Supply. Too cheap. Installed points and condenser from NAPA and haven't had any issue for several years. My 300 is 12v with 12v coil, no resistor needed.
 
Quality parts are a real problem but this issue of resistor or no resistor just constantly goes on and on in this forum. The reason manufactures came up with the idea of an external resistor instead of using a straight 12 volt coil was to obtain better starting. That does not mean it won't start with a straight 12 volt coil, it means that when you make thousands of tractors, the odds are heavily in your favor to provide an improvement by using the resistor and a bypass system during the cranking, starting process. It has been used by almost every manufacturer of gasoline engines now since the late 50's. It works but requires an understanding of what is being done. You need a source of full battery voltage during the cranking process. This is obtained by a simple addition of a bypass terminal to the starter solenoid in most cases. All battery voltages decrease during starting so it just makes good sense to provide the hottest spark during cranking by using a resistor and a bypass. Does nothing for you once engine is running and starter is disengaged.
 
"Plus, once you have filed points, they are JUNK, only good enough to get the tractor back to the yard, for convenient point replacement.

I will get flamed for that comment, but it is true, most of the time."

Hey Bob I WONT FLAME YOU I agree 100%

Once that shiny silvery coating is gone from too much filing, youre down to soft steel which will burn and pit and carbon up in short time YOURE RIGHT

John T
 
like said, probably on the coil change you got the wrong one.
If you bought one of my tractors which all run the IC14SB coil that needs no resistor, and replaced it, and just asked for a 12v coil, the store would probably hand you one that needs a resistor= burnt points.

or possibly the new coil didn't spec right.
After getting 'burnt' lol a few times, I ohm them all.
This after buying an offshore 12v no resistor needed coil....that my ohm meter showed 1.6

also, agree with Bob. While I sometimes file points on old junk.
(do what ya gotta sometimes)
I also mark the distributor cap with a paint pen, so I remember I did it on that tractor.
Because it will probably need filing again every time I use it....

also, even though a dead battery would be the obvious first sign, check that ignition switch.
a randomly/sporadic failing switch that 'leaks' current to the coil after you walk away will burn points up pretty quick if they stop closed.
 
There can be a few (and more) reasons for premature point failure.

1) Excess coil current, it should be in the range of 4 and less amps.

2) Weak or completely open Condensor or one that's not the right size (MFD Rating).

3) Coil with too low LV Primary Resistance (thus allowing more then 4 amps of current the points have to switch)

See if that coil has a LV primary winding resistance (between little + and - terminals) of around 2.5 to 4 ohms????????? If so it should be fine on 12 volts no ballast required. If its way less, like 1.2 to 2 ohms IT NEEDS AN EXTERNAL SERIES VOLTAGE DROPPING (12 TO 6) BALLAST RESISTOR otherwise the points will burn up quickly.

A 12 volt coil may be labeled "12 Volts" or "12 Volts NOT for use with Ballast" HOWEVER if tis labeled "12 Volts requires Ballast resistor" its a 6 volt coil and needs the ballast or it will run hot and the points burn up quickly.

I suspect the coil may be a 6 volt unit or needs a ballast resistor therefore its causing excess current burning up the points or else the condenser is bad or open or not wired correct or the points are just junk quality

John T
 
I connected mine to the terminal where the 12V wire goes between the distributor and the coil, then trapped the tab on the second condensor under the coil bracket.

Greg
 
I may be getting a bit technical here, but John T. is correct above in stating that:

"2) Weak or completely open Condensor or one that's not the right size (MFD Rating)."

Size or capacitance value of a condenser is rated in microfarads (MFD). If the original condenser is of the correct MFD value, installing a second one will add the values and give a wrong rating,with results as indicated above.
 

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