Help with the starter motor?

[Bitter]

Hi all, I'm trying to help my friend get her tractor started for sale and it's giving us a bit of a hard time. It's always started...except now that someone wants to buy it!

So far heres whats going on,
1.starter turns the engine easily with the spark plugs out but the starter seems to get pretty warm pretty fast

2.with the plugs in it will turn the engine a few times but more slowly and then get very slow and not turn at all

3.the negative battery cable was getting a bit warm so I ran a redundant along next to it and grounded it directly to the starter casing to ensure it was getting a very good connecting. the positive cable is very heavy gauge all the way and stays cool, the negative is still getting a bit warm at the battery.

4. i remove the metal shield around the brush end of the motor and the commutator looks pretty worn and there was a lot of powdered copper inside there. i did not touch anything in there yet, not sure what i should be touching.  i turned the key with the cover off and the brushes seem to run roughly over the commutator, when it does not turn the motor just twitches when you turn the key.

5. i jumped the solenoid posts (the solenoid is not the original one, someone has done some wiring work) with the head of a ratchet and the starter behaves the same way, the solenoid seems to be good.



I'm thinking that the starter motor is shot or on its last legs, but I wanted your opinion of the situation. Also, I have no clue how the motor comes off the tractor.  I work on cars, their starters have bolts that hold them, I don't see any bolts holding this to the bell housing.  I'm a little lost on this one.  If i remove it, theres a local company that does rebuilds on starters and alternators/generators and electric motors for the shop i work at, I would just ask them to rebuild it.  I see a starter listed on ebay, but I still don't see how it attaches to the engine exactly.  Thankyou for your time, and I hope you all can give me some help on this!  she needs it sold to help pay her property taxes

[Bitter]

got the starter off, local place rebuilder told me how. such a dummy i am! it was the 2 long bolts that hold the motor together that also hold it to the tractor. the bendix doesnt seem to work correctly, it seems to be stuck partially out.

i really hope its just a bad starter and not anything else, its always been very slow to crank but started always.  plugs looked a little on the black side of rich/lean but since its being sold i'm not worried about it.

[Pete P.]

Bitter --

Sounds like you've got your answer on the starter -- it sounds pooped and rebuilding it is in order. You didn't say what model of tractor you're working on, but I'm a bit concerned with your comment that the "negative cable gets hot" and that the negative is the ground. 

Assuming you're on a model N -- probably 8N because of a soeleniod being present -- it's supposed to be 6v positive ground.  That said, lots of people have converted them to 12v neg ground over the years.  You say the tractor cranks slowly, though -- 12v conversions almost never modify the starter and a 6v starter spins pretty fast on 12 v. 

So, if the machine is still 6v, switch the ground back the right way and repolarize the generator.  Also, make sure that the ground (positive) is either a strap -- which is proper -- or at least zero gauge wire.  00 (double-ought) is better yet.  The hot side (negative) should be similarly large, either AWG 0 or 00.  Heat means there's too much current going over the wire -- as this occurs the resistance increases dropping the voltage delivered AND making more heat.  Not a good situation for fire safety or performance.

If the machine is 12 v, you still have a resistance problem in the ground.  A strap ground is still superior, but one can get away with AWG 2 on a 12 v system. 

I know you're selling the tractor, but if she was originally 6v, I'd have the starter re-wound for 6v.  That way you'll keep the original heavy windings which will work on either voltage and last longer.

Hope this helps,

Pete P.
Harborcreek, Penna.
 

[lha]

Make sure you clean the mounting surface on the bell housing and the 'tube' where the back plate contacts it ,as these places effect the ground.The starter MUST have a GOOD ground to spin properly.Mine,'41-9n,works very well and is 6v+g,starts well everytime,90*-10*. Grounds must be clean&tight.---lha