Farmall Cub

We just got to the point of starting our restored cub. Motor has been totally rebuilt. I have a 6 volt battery, magneto, eyc, but the 6 volt ill not turn over fatst enough to start. Hook it up to 12 volt and it starts in abut 2 seconds every time. Can I run a 12 volt battery instead of 6 volt and just hook it to a manual battery charger occasionally? Should I convert to a 12 volt charging system and leave the mag and starter as is????

A suggestion would be to: test the 6 volt battery . you can check for a dead cell by removing the battery caps and watch to see if a cell bubbles while cranking . this would indicate a dead cell .the new engine maybe tight and require some break in..

What do you have for battery cables? Do they get warm when you crank the starter?

check for bad grounds on the cables and starter to block also, with all the new paint it could be a problem
Tim

Good suggestions, I don't have it all wired yet, just using jumper cables so it probably ain't heavy enough to get it to crank. Just noticed that the 6 volt will barely even move the starter a half round at a tine VERY slowly but a 12 volt will make it spin like a top! Didn't think there should be that much difference so I was curious,,

John, I would recommend your negative cable to the starter being a #2 gauge wire or larger as Bob was pointing out. On your positive ground side, a flat braided cable found at many farm and home stores works and fits well inside of your battery box. Good grounds and connections as already mentioned is important.

oh and since you are breaking in a new rebuilt engine, be sure to retorque the cylinder head bolts after some run time and getting the engine hot, if you have not already.

Also, when cranking the engine, don't push in the clutch. Leave the Cub in neutral and the clutch out. It will spin faster that way.

Yes sir Brian I will check all that. My ground will be a replacement flat. Cable from tm tractor and my starter cable is the one I got from rock auto that Tim (Tst) suggested that is a 2 ga. Just need to get a right angle battery terminal but can't seem to find one

Thanks barnyard, that how we are doing it with the tractor in neutral

The 2 gauge cable is too small for a six volt system. The 2 gauge cable that most auto parts stores sell is for a 12 volt system, not 6 volt. For a good working/wired 6 volt starting system use 0 gauge or bigger. Also remember, you have to have the same size coming and going, the ground needs to be the same gauge as the power. Six volt is a lower "pressure" system, so you need a larger diameter "pipe" to move the correct volume. I have been driving antique 6 volt vehicles for more than 50 years (model A's and T's, Dodge Brothers, Packards-straight 8 cylinder with high compression) and 6 volt works fine, so long as it is wired correctly and all the components are in good working order. Go through the entire system and make sure that everything is up to snuff, not just a part of the system, the whole thing. Twelve volt is an easy way out.

Wiring- correct gauges, no shorts, all connections bright and tight

Battery- Don't assume it is good, test it. If buying new, check the date code and have them test it before you leave the store

Generator- Check the brushes, brush springs, does the commutaor need to trued and undercut, is there an internal short in the windings or armature (growler and Megger test), is the drive belt tight enough. Do not trust the gauge in the instrument panel, check the output with a quality meter, check the bushings and bearings. Once running, be sure to polaraize the generator properly

Cut-out or Voltage-Regulator- open it up and clean and inspect the points, make sure that the air gap for the points are set correctly. As long as ther is nothing damaged or broken, these can be fixed

Starting motor- Check the brushes and brush springs, does the commutator need to be cleaned/trued, is the Bendix spring weak, is there an internal short in the windings or armature (growler and Megger test), as with the generator, check the bushings and bearings(spinning free with no drag)

I have logged a lot of miles on 6 volt systems, 4 different trips coast-to-coast in a model T alone, and so long as the system is good to start with and it is taken care of (just like you should be taking care of a 12 volt system) it will work perfectly. Whether you stay with 6 volt or switch to 12 volt, it is your decision, it is your tractor. Just remember, 12 volt components will wear out as well. How well do you think they will work in 50 years without proper maintenence? Neither 6 or 12 volt is more reliable, just different voltage.

My 48 was cranking slow on the six volt battery so I put new brushes and bushings and springs in it. It still cranked slow with the six volt but when I hooked up a 12 volt it would fire right up. Come to find out it has a red tag on the sarter not a black tag. I red on here that the red tag is a 12 volt starter and the black is six volt starter. So my conclusion was12 battery will spin a 12 volt and a six volt just fine but 6 volt battery has a hard time spinning the 12 volt starter.

64/67lo-boy wrote:My 48 was cranking slow on the six volt battery so I put new brushes and bushings and springs in it. It still cranked slow with the six volt but when I hooked up a 12 volt it would fire right up. Come to find out it has a red tag on the sarter not a black tag. I red on here that the red tag is a 12 volt starter and the black is six volt starter. So my conclusion was12 battery will spin a 12 volt and a six volt just fine but 6 volt battery has a hard time spinning the 12 volt starter.

Very excellent point. Make sure that you are starting with the correct components.

A newly rebuilt engine will usually turn over a lot harder than one that has been run a little. Maybe a couple hours of running will take care of the slow cranking. One other observation, a Cub engine doesn't need to turn very fast to start. They can be easily started with a crank. If it doesn't start when cranked slowly, it may need a tune-up,or in this case maybe the point gap, timing, wiring etc. needs to be rechecked.

A properly rebuilt engine will not be that hard to turn over. If it is, there is a problem with the rebuild.