300 U 12Volt conversion pulley question

[Paul 300 U]

Hello. Picked up new 12 volt coil with
internal resistor yesterday and got started
today. Battery is out, Anmeter wires
switched, generator out. It's obvious pulley
length is short on new alternator. I started
trying to switch pulleys but don't want to
break anything. My questions. What's the best
way to remove the pulleys. And. Will
switching the pulleys fix the length issue.
Thanks! Paul

 

[Janicholson]

The most common method is to use a threaded rod or long bolt for the mount so that the existing pulley is aligned by having the alternator closer to the radiator. A piece of 3/8 pipe or tubing can be used to make a standoff to set the distance (adjust with washers). The farmall pulley will not fit the metric Hitachi shaft at all.
The new coil will not have a resistor in side it. it is just wired for the increase in voltage. The 6v coil with resistor is like buying a 120 volt light bulb and putting a resistor in series with it to use it on 240. The coil you purchased has thinner and twice as many of the primary windings. The reason there are coils with resistors in the circuit is so the resistor can be bypassed for increased starting voltage as the starter draws down the voltage. Jim

 

[used red MN]

I do not know if you got a complete kit that has a mount or not. If not often times the original generator mount can be flipped over and then allows for better pulley alignment and also helps with hood clearance. I have more experience with a Farmall M but I think the same applies.

 

[charlieu]

You are going to find that the pulley of the old generator is not going to fit the Hitachi alternator. The shaft size of the generator is 17 mm and the Hitachi alternator shaft is 15 mm.

 

[fastfarmall]

Buy a bracket from Charlie U,it will fit perfect!

 

[ShakerPrairie]

(quoted from post at 22:20:54 12/27/23) Buy a bracket from Charlie U,it will fit perfect!

That would be your best bet.
His stuff fits and works very well.

 

[Paul 300 U]

Thanks Jim
I should have realized the shafts would be different since the nut was metric. If my local hardware store has the material I'm going to use your suggestion for the bracket. I don't have too much the time for trial and error but figuring it out is part of the fun. I can always buy a kit if needed. Thanks for the info on the coil. The instructions say no external resistor required so I made the uneducated leap that their was an internal resistor. Paul

 

[Paul 300 U]

Used Red. I bought the alternator over a year ago then decided to shine connections etc and buy a new 6 volt battery. In hindsight I probably should have bought the complete kit. I think I also got caught up on wondering whether I should install an electronic ignition as well. Thanks Paul

 

[Paul 300 U]

Thanks fastfarmall. If I can't make Jim's suggestion work I'll give the special bracket a try. Paul

 

[Paul 300 U]

Charlieu thanks! You all saved me lots of
trouble trying a solution that wouldn't work.
I may be in the market for custom bracket.
Thanks Paul

 

[charlieu]

Here is a picture of the mounting brackets that I make for installing a Hitachi alternator on the Farmall tractor. This is bracket is for the Farmall H. A bracket for the 300U would be very similar, I just could not find a good picture.