Friday, May 2, 2014

Retrofitting a Kubota B6200 Tractor ... or ... Percolator to Water Pump

In the early days of Kubota, many of their machines were designed with a percolator cooling system. My Kubota B6200 is an early model and indeed, one of those.  While it's been a great machine, the radiator sprung a leak and you cannot find the radiator (or easily find a shop anymore that will fix them).  You see, pre serial number 60000 used the 15751-72060, while later ones used 15531-72060 (the big difference you can easily see is that the early ones have the top hose connection straight in while the later ones have the top hose coming out at a 45 degree angle).  In looking into the situation, I found a junk dealer that would sell me the parts to change the front gear cover so it would have a water pump.  Some lessons learned include:
  • your going to need to build 2 custom tools out of sockets (more on that later).
  • using heat to expand parts works better than anything for removing stuck parts
  • use taps and dies to clean all your bolts and threads before putting everything back together.
  • The fitting in the side of the engine is a 1" 11.5 TPI part, so instead of buying a tap and die to fit those, to clean up the threads, I bought regular pipe nipple and cape, and cut grooves into them and made a poor man tap and die.
  • Use Messicks for parts (they send parts breakdowns in PDF ... very handy).
  • don't rush.
Tear down:

For tear down, drain the oil and water.  Use an impact wrench for most of the large bolts.  The hardest part of the tear down was the harmonic balance wheel (060) and front PTO flange assembly (090).  The mechanic told me they slide right off, but mine were too tight for that. When you get the radiator and front grill off (you need the room, so spend the extra hour and remove them), you take out the three bolts on the front PTO flange (100 & 110).

Now you have to put a torch on the PTO flange and get it good and hot.  Then, I tapped the top front of the PTO splines, rotated the crankshaft 90 degrees and tapped it again, then another 90 and tap ... and just continue until you see the flange start to separate from the harmonic balance wheel.  Then, I slide a large flat tip screwdriver between the two and both pried there, as well as grabbed the flange with gloved hand and while rocking the flange, pried them apart (no rust ... just a tight fit).

Then, remove the center bolt on the harmonic balance wheel and use a wheel puller to get it off. Again, a mechanic told me it too slides off, but I needed a wheel puller.

Once those are off, you start taking off all the parts that obviously come off.  The parts you'll need are:

From Autozone, a Duralast 15340 V belt (old one is 31" ... you need a 34" belt)
15531-72060 - Radiator (got mine from a junk yard, but new ones are available for a few dollars more)
15752-04020 - Gear case front (got mine from a junk yard)
15531-72910 - Water Flange Assembly (got mine from junk yard)
15973-64010 - Dynamo (old one will not work ... junk yard part also)
16851-73270-620 - Thermostat Gasket
15676-73430-620 - Water Pump Gasket (replaces 15531-73430)
15676-04130-620 - Gear Case Gasket (replaces 15676-04130-620)
15296-88130-620 - Engine RPM sensor (replaces 15221-88130)
15263-72920-620 - Water Flange Gasket (replaces 15261-72920)
04811-06130-620 - 3 each ... O rings
15531-73013 - Thermostat
15531-73350 - Top Return Hose
15752-72850 - Bottom Return Hose (short one)
15877-04140 - Crankshaft Oil Seal
15752-72940 - Radiator Hose

The hardest part was the crankshaft oil seal.  You see you need both the newer one and the older one.  You remove all the rubber from the new one, tap or press it in, and then the older style smaller one presses into that.

As long as all surfaces are clean, you won't need any RTV or gasket sealer.  Torque all 10MM bolts to 7 ft lbs and nothing leaked.  Pressure test your new radiator ... AutoZone rents out pressure testers for a deposit, but free as you get the deposit back.

Runs great.  Nice and cool.


  1. Thanks for sharing!

    The Kubota tractor range offers the ultimate in reliability, fuel economy, performance and versatility. With Kubota part dealers and service centers available in the market its makes us easy to deal with Kubota parts and its problem. In which Country Sales & Service an authorized Kubota engine service center, they offers engine rebuilding & repair, part sales or custom power units built to spec in U.S. & Worldwide.

  2. THANK YOU! I've scratched my head over that harmonic balancer all night. (Now, where's my torch).


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