Need a bigger alternator for B series Kubota's

   / Need a bigger alternator for B series Kubota's #1  

TJP440

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Nov 5, 2007
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Tractor
Kubota b3200 & GR 2120
I just finished what I believe and hope is the last upgraded alternator on my B3200. I believe this mod will work on other b series units as well but I'm not 100% sure.
This all started last year when I decided to add a cab for winter work. The cab came with a FREE 300W heater. Hot idea (pun intended). The problem is the little dynamo only puts out ~ 14 amps. Hmm 300W at 14V = 21A. We have a problem Houston :(
So, I researched here and elsewhere for solutions. I did find that Kubota had offered a 40A? alternator upgrade that was used on their cabbed models but they were no longer available. And being a tight a-- , I kept looking. I did find a thread on here that someone had done a 60A upgrade but could not locate a source for the suggested alternator.
OK, so I bought a couple of different units off amazon but could not get them to function properly using the charge lamp.
So, I resorted to my hot-rodding roots and found a 90A mini alternator that was a single wire hook up and added a small digital meter to monitor the V. A small amount of fabrication was required and we were jamming. :) I also upgraded the charging system wiring as needed.
So, then I get to thinking if I have all this power available why not add another heater?
I found an airplane cabin heater that puts out~ 650W. That should do it and the total draw is well under the 90A the alternator is rated at. So, I proceed to install the added heater, wiring, fuses etc. and all is well for about 3-4 hours. In the middle of summer with no real load on it the alternator dies. OK replace it under warranty. Second one same thing. A bit of googling shows the alternator was originally a 55A denso unit that is being copied by you know where and sold as a 90A.
More research results in a GM CS121 alternator rated at 120A being sold by reputable sources. It appears bigger but actually fits better. Minor mod's again are required.
I am more confident than I was before as the unit is actually made here in the US and is a well-established company.
Sorry for the pic's as they were an afterthought. If anyone is interested, I can provide better pic's and more detail
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   / Need a bigger alternator for B series Kubota's
  • Thread Starter
#2  
I am cutting and pasting from a post i put up on another site that requested more information so here it is ;)
The alternator I am currently using is a Tuff Stuff performance CS121 GM style Part # 7937.
Alternator Link
Current pricing is about 130.00, do you shopping though 😉
Mod's required:
1. Remove existing dynamo and dipstick
2. I slotted the lower mounting hole on the alternator about .200" to lower the alternator and accommodate the previously modified adjustment bracket. This may or may not be required on your unit.
3. The alternator was then mounted with a 5/16 x 18 x 3" ? long bolt. A spacer approximately 1" long was needed to move the alternator and align the pulleys.
4.The adjustment bracket previously modified consisted of cutting off the existing mounting holes. I then cut a piece of 1/8 inch ¾ or 1 " angle about 2 " long and added the holes for mounting it using the two bolts directly below the thermostat (10mm heads) . I did have to notch one side of the angle to clear the T/stat.
5. I removed the LF engine lifting plate and bolt for added clearance.
6. The Alternator was then rotated against the block and the previously cut slotted adjustment matched up to the angle iron piece fabbed in step 3.
I angled the end of the adjusting arm to follow the correct arc/travel for adjustment of the belt. A short 6/16's ? spacer (LOL 3/8) was used between the adj. bracket and alternator with the bolt entering from the back.
7. The two pieces were then welded together.
8. The shortest belt possible was used which required slipping the alternator in at an angle from the rear and then installing the lower mounting bolt and spacer. Don't have the belt number handy but I can provide it if needed. It may be different than your unit though.
9. I ran a 6 ga wire from the alternator to the starter stud.
10. The dipstick was slowly tweaked to clear the alternator etc. and reinstalled with a small amount of sealer and the mounting tab to the same location.
11. Remove the instrument cluster.
12. Disconnect the existing voltage regulator. Remove the charge lamp indicator bulb.
13. I then installed a small digital meter and tied into the main battery feed at the ignition switch Digital meter
A pretty simple deal if one has basic mechanical skills and fabrictaion abillities. I can provide more pic's but my time is extremely limited so patience will be required. Hindsight being 20/20 I should have taken measurements and pic's as I did it :( 🍺
 
 
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