Cub won’t start on 6v

[DoubleJFarmsWA]

So, a cub that I have been working on (someone else started restoring years ago), I have gotten repaired and running. I have not been able to try and hand crank it, as the hand crank needs some repairs. But, with a 12v battery (I believe, its 6 volt pos ground system, as it has a generator on it), it’ll crank and start right up, but if I connect the 6v battery to it, it will not start. I believe the battery cables are small for 6v, but it cranks it over faster then hand cranking will, so any suggestions on where to look?

[Don McCombs]

6v batteries depend on clean and tight connections, especially at both ends of both battery cables. Also check the condition of both cables. Internal corrosion will significantly degrade the function of those cables.

[Barnyard]

Everything Don said and make sure you use #2 gauge or heavier copper wire.

[Eugene]

Battery cables and connections as previously stated.

Another likely cause is the bearing/bushings in the starter are worn allowing the armature to drag on the fields. Easy DIY repair, include new brushes.

[Jim Becker]

Six-volt systems don't spin an engine at 1,000 rpm like you typically see with a 12-volt system. You say "it cranks it over faster then hand cranking". Maybe what you are seeing is totally normal. If everything is right, they start with a hand crank. So your 6-volt battery is spinning it fast enough so it should start. Maybe your problem is somewhere else, not the starter. How is the compression? the spark? the timing?

Does it have a magneto or battery ignition? If battery ignition, problem areas others have mentioned will cause a decrease in spark while cranking. This may keep it from starting even if it is turning fast enough.

[DoubleJFarmsWA]

It’s magneto. I think the timing is good, once I get it started it runs good, sounds good, seems to have plenty of power, idles nice. The Neg battery cable to the starter is not a #2, so I’ll get that replaced and see if that helps. With 12v spinning the starter, it fires right off.

[Barnyard]

The Neg battery cable to the starter is not a #2, so I’ll get that replaced and see if that helps.

I use welding cable, it flexes better.

[ArtB]

I had a similar problem, In my case the commutator needed cleaning and new brushes. Thread at: viewtopic.php?f=1&t=116440

[ricky racer]

I think you'll find upgrading the battery cables will make a world of difference. I too use welding cable.

[inairam]

6 volt batteries with AWG 2 cable and clean connections will work great. the 6-volt batteries usually have more CCA than the same size 12 volters.

My 6-volt cubs are my best starters.

[Matt Kirsch]

I'm going to go down a different rabbit hole and suggest the magneto impulse.

With a hot magneto on proper time, you should be able to fart in the tractor's general direction and have it start.

If you are not hearing a distinct "snap" from the magneto as it cranks over slowly, the impulse is not working. 12V spins it over fast enough for the magneto to generate a hot spark without the impulse.