Correct fan belt

All,
The main reason my TO-20 is torn down, is that the water pump pulley split and I had to replace it. So decided to convert it to 12v at the same time. In searching the net for the correct replacement belt, I have come upon an issue I have not been able to solve. When trying to purchase a new belt (the old one shredded) I am finding two different belts with the same part number. One belt is 5/8 in wide and the other is 7/8 (actually 13/16 inch wide. The 5/8 fits too deep in the pulleys with barely 1/16 before it bottoms out in the pulley. The 7/8 sets too high in the pulley with about 1/8 in outside the pulley circumfrence. It looks to me that the correct belt should be 3/4 in wide. However no one seems to make a belt in that thickness. I searched the archives and did not find an answer as to which is the correct belt. Normally this would not be a problem, but my tractor has a waggner loader with the loader hydraulics driven from the front pulley. It is quite a evolution to change the fan belt. So I want to make sure the belt I install will not need replacing again anytime soon. At this time I am planning on using the wider belt figuring the wider belt will wear and settle deeper into the pulleys. Since I can not find the correct width belt,this appears to be my best option. Any reason why I should not use this approach?

A "B" section industrial belt is 21/32 wide and 13/32 tall. That might run a little higher than the 5/8, and the shorter height won't bottom in the pulley. A "BX" designation will get a grooved inside, more flex for going around the alternator pulley.

Steve, Thanks for the reply. I was running a B series belt. What I have found is that the pulley that came with the alternator conversion was wider than it was supposed to be. I acquired a little larger diameter pulley and checked the belt. That pulley fits perfectly either a 5L or B series belt. The 5L is a little thinner, so it will not set as deep in the pulley and I do not have to worry about it bottoming out on the pulleys in the near future. I will have to machine a little off the back of the pulley to get the belt to line up properly, but that is not a problem. The alternator kicks in and starts charging just a little above idle with the larger belt, so it should work well with the smaller pitch diameter of the 5L belt even though it is turning a little slower. I still like the idea of a thicker belt that would possibly last longer, but the belt is only running the water pump and alternator. I do not have any lights or other loads besides the ignition system, so it should last quite a while.

Mitch

All,
Got the new pulley and belt today. I had to machine a bit off of the back side of the pulley for it to line up correctly. No problem, about 15 minutes at the lathe. I ended up going with the B series belt. Specifically BX37 (available at NAPA). With the larger pulley, and with a partially discharged battery, the charging current drops back to about 10 amps around idle, when the revs are increased to around 1000, then the amp meter indicates full output (approx. 30 amps). The replacement pulley is 3in in diameter. Not perfect, but it should work well. I did end up having to order a new starter for it. The original starter worked for a short period of time after the 12v conversion. I kept the starting times to 5 seconds or less. Anyway, it died, so I purchased a new 6v starter. It hasn't been in the machine over a week and it died today. Much the same symptoms. Now I'm ------. So back to the computer and order a 12v starter from this web site. Should be here sometime next week since we are in the same state. Hopefully that will resolve the dying starter problem. I haven't taken the starter apart yet to figure out what happened. Just so it is clear, the tractor starts and runs fine. I was using the starter to turn the motor over during some testing. I was being careful to keep the starter usage short. 5 seconds should not have been enough to overheat the starter.

Mitch

Well, the new starter arrived, and was installed. Everything was looking good. Then today while turning the engine over, the starter made the same noises as the previous two starters, then promptly died. Now this was a starter that I purchased from this web site that was supposed to be a 12v starter. Sent an email. Hopefully hear something tomorrow about returning for an exchange. At this point I am thoroughly discouraged. I'm thinking of just going back to the 6v system. I can replace the voltage regulator in the one wire 10SI alternator with a 6v one, remove the ballast resistor from the ignition circuit. That should resolve the starter issue and still give me the benefits of an alternator. Of course, the 12v lights I was going to install will have to find another purpose.

Mitch