"To turbo or not to turbo, that is the question"

pigdoc

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G1800S L2500
Aug 19, 2022
275
203
43
SE Pennsylvania
Hi Folks,

Recently, the subject of turbocharged Kubota engines has come up repeatedly.

I am in the market for an older, 20th century, L-series tractor, and have become somewhat obsessed with what opportunities might exist for that tractor to be powered by a turbocharged 4-cylinder engine.

Why? I don't have a defensible reason for my preference, it's really just a whim, at this stage. But, I have been highly motivated to do some research on this topic, and that's what I want to share here.

I started by asking a question - "What Kubota L-series tractors were produced in the 20th century with turbocharged 4-cyinder engines?" For the US market, the answer is simple: "None." For the "gray market", the answer gets more interesting. I have found three or four Kubota tractors produced for non-US markets that were factory-equipped with turbocharged 4-cylinder engines:

- L4202 (1978-1985)- came equipped with the VT1502 engine, rated at 42hp, in contrast with the non-turbocharged V1500, V1501, or V1502 rated at about 35hp.
- L1-435 - equipped with the V1512-DI-TI-N engine(?), rated at 43hp
- L1-43/GL43 - equipped with a 4-cylinder turbocharged engine, unknown model

Here is an L4202 data plate:
1674828554593.jpeg


One can search these model numbers in youtube, and find videos of them in operation, mostly in southeast Asia. I'm not sure if the V1512-DI-TI-N or V1512-DITC engines seen in these videos are factory-installed, or transplants. The V1512 engine was also used as a stationary powerplant (irrigation pumps, generators, etc.).

I have obtained a Parts List for the L3202 and L4202 tractors, and it includes part numbers for all engine parts for the non-turbocharged V1502 and the VT1502. What are the differences in these two engines? Besides the obvious (turbocharger and turbo compensator), they are:
- cylinder head casting
- piston and piston-ring assembly
- crankshaft
- connecting rod bearing [connecting rod part numbers are the same.

I am guessing that the crankshaft is different in that the rod journals are radiused, thus requiring a different connecting rod bearing. I have attempted to document the differences between the turbo and non-turbo cylinder head and piston. Here's what I have found:

V1502/1702/1902 Cylinder head casting (non-turbo):
1674828688910.jpeg

VT1512 Cylinder head casting (turbo, 15345-03040):
1674828839526.jpeg


It is easy to see the important difference here. The non-turbo head is an Indirect Injection head, with a spherical pre-chamber ported into the combustion chamber between the valves. The turbo head is a Direct Injection head. The injector nozzle protrudes through that chamfered hole between the valves.

Here are the two pistons:
1674829167470.jpeg

The top piston is for V1512 (non-turbo) and the bottom piston is for the V1512-T. Notice that valve reliefs are missing from the turbo piston, and that it has a bowl in the top. The injector nozzle is centered in that bowl. Strangely, the injectors for the V1502 and the VT1502 in the parts list are apparently, the same (see below).

At this point, I want to introduce a very informative scientific review paper which discusses the engineering intricacies of turbocharged diesel engines. The title is: "A review of design considerations for light-duty diesel combustion systems" The two co-authors are at Lund University (Sweden) and Sandia National Labs (Livermore, CA).
Here is a link to the paper:

My favorite quote from the paper is:
"Thousands of man-years of effort have been expended in balancing multiple trade-offs as such basic parameters as compression ratio, bore-to-stroke ratio, and combustion chamber geometry are selected."

What I learned is that there are intricate design features of the piston bowl (into which the injector spray is placed) and its companion injector which have profound effects on the efficiency of combustion. Also, the piston height is greater in the turbocharged motor - it is what is known as a "quench" motor, where the piston approaches to within 0.6-0.8 mm of the cylinder head. This allows heat to more efficiently be transferred from the piston to the cylinder head and its water jacket. The space between the piston margins and the cylinder head is unavailable for combustion. The purpose of the bowl is to create "swirl" in the cylinder to improve mixing and combustion efficiency. The injector spray pattern must be carefully matched with the piston bowl.

Besides the piston and cylinder head design differences (turbo vs non-turbo), Kubota injector pumps are different for turbocharged engines. There is a turbo compensator, which adds additional fuel as boost increases to maintain the proper fuel-to-air ratio. I am not sure if the timing of Kubota injector pumps can be finely adjusted, but I know that it is infinitely adjustable with turbocharged Cummins motors. Timing should be retarded for turbo motors, because combustion is a more rapid event under the conditions of higher cylinder pressures and swirl.

Bottom line here is that simply slapping a turbo on a non-turbocharged engine ignores ALL of this...and is thus, a fool's errand. YMMV.
Yeah, it'll make a cool noise, but will it make more power?
Practically speaking, I see no opportunity to properly convert a non-turbo engine to turbo.

SO, then what???

Given that it would be very difficult or even impossible to get my hands on one of these gray market tractor models, and ignoring the challenges of parts support, what else can be considered?

I'm starting to think more and more about opportunities for engine swaps to turbocharge a non-turbocharged tractor model. It's attractive to consider the prospect of installing an entire engine to grab all the matched turbo-engine features at once.

What I'm looking to document now is the differences between the mounting systems at the bellhousing between readily available, domestic turbocharged Kubota engines, and the tractors I might want to install them in. So far, I've sifted through skid-steer loaders, to find the turbocharged 4-cylinder Kubota engines. Here's what I've found:

Bobcat 773 (1994-2001): V2003-T-E2B (46hp)
Bobcat S160 (2005-2013): V2003-M-DI-T (56 hp)
Bobcat S185 (2002-2013): V2003-M-DI-T (56 hp)
Bobcat S205 (2005-2013): V2403-M-DI-T (61 hp)
Bobcat S550,S570 (2013-present): V2403-M-DI-T (61 hp)
There are other Bobcats with larger turbocharged engines (V2607-T, V3307-T, V3800).

Yesterday, I looked at a Bobcat S185 and a S205 side-by-side. Interesting that, on the V2003 motor, the injector pump is on the right (radiator) end of the engine, and with the 2403, the injector pump is on the left (flywheel) end of the engine.

My thinking is that, if the bellhousing mounting pattern can be made to fit (modified or adapted), other things (like engine mounts, radiator location) are relatively easy.

-Paul
 
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Rdrcr

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May 7, 2021
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^^^^
Nice writeup and great information!
Thanks for sharing.

The theory behind the analysis is correct and in the best case scenario, I agree, having specifically designed components to handle the increase pressures and temperatures of a Turbo system is worthwhile. A manufacture can easily absorb these costs during development. Additional fuel is an obvious requirement for any Turbocharged application. Injection pump timing adjustments would be dependent on the specific engine application. Some would require adjustment, while others might not.

Ultimately, however, none of the information presented, means that a Turbo cannot be added to an engine and produce additional power safely and effectively.

Several forum members, including myself, have added Turbochargers to their tractors and have enjoyed the benefits for hours upon hours of trouble free operation, but, it's not for everybody.

Mike
 
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JeremyBX2200

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BX2200
Aug 3, 2020
440
424
63
Indiana
If this is a "Because I want to and think it would be fun" project then I say go for it!! Nice research on finding turbo Kubota engines.

For the size engine and hp/torque output range that is possible I would be interested to see what the difference would be between turboing an existing NA kubota vs using one of these factory turbo engines.

It is true that the DI is superior to IDI and piston design matters, but I knida get the feeling that this means more in the end result for larger more powerful engines.

There is a guy here that turbocharged his L. THe thread is linked below. Turboing could help tractor performance in certain situations, but due to the way different systems work you would not get the same effect as a car/truck.

Just my 2 cents. If you decide to do this I will be following your build.

 
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JeremyBX2200

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BX2200
Aug 3, 2020
440
424
63
Indiana
^^^^
Nice writeup and great information!
Thanks for sharing.

The theory behind the analysis is correct and in the best case scenario, I agree, having specifically designed components to handle the increase pressures and temperatures of a Turbo system is worthwhile. A manufacture can easily absorb these costs during development. Additional fuel is an obvious requirement for any Turbocharged application. Injection pump timing adjustments would be dependent on the specific engine application. Some would require adjustment, while others might not.

Ultimately, however, none of the information presented, means that a Turbo cannot be added to an engine and produce additional power safely and effectively.

Several forum members, including myself, have added Turbochargers to their tractors and have enjoyed the benefits for hours upon hours of trouble free operation, but, it's not for everybody.

Mike
Beat me to it. I linked your thread in my response.

I will be interested to see the PTO dyno results you get
 
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Rdrcr

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^^^^
I'll be posting those results soon. I'm currently in the process of writing my conclusions on the setup and the results we recorded.

Mike
 

North Idaho Wolfman

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I can point out several issues in trying to use a motor from a non Tractor setup.

#1 killer is the drive for the hydraulics for the tractor, Non AG tractors do not have the drive, and it's not as simple as bolting it on, it's the fuel cam.
If the engine was never made for ag use there will not be a fuel cam available.

#2 The crank journals and bellhousing mounts changed from the 02 to 03 series of engines.
They got bigger and you would have to machine the bellhousing to fit if it even will.
There is also many differences in the V1502 (very early motor design) to a V1902 (very late motor design).

#3 You would also need to make sure the oil pan crosses over because there are differances between ag and non ag use.

I've pointed out in the past that you could easily take a L3450 with a V1902 DI and turbo it without there being an issue.
The motor is using the same parts as the turbo.
I've done swaps from a V1702IDI to a V2203DI in a 743 BOBCAT and was lucky enough not have to deal with the hydraulic drive issue or the Bellhousing issue.
 
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jyoutz

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MX6000 HST open station, FEL, 6’ cutter, forks, 8’ rear blade, 7’ cultivator
Jan 14, 2019
2,458
1,565
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Edgewood, New Mexico
Hi Folks,

Recently, the subject of turbocharged Kubota engines has come up repeatedly.

I am in the market for an older, 20th century, L-series tractor, and have become somewhat obsessed with what opportunities might exist for that tractor to be powered by a turbocharged 4-cylinder engine.

Why? I don't have a defensible reason for my preference, it's really just a whim, at this stage. But, I have been highly motivated to do some research on this topic, and that's what I want to share here.

I started by asking a question - "What Kubota L-series tractors were produced in the 20th century with turbocharged 4-cyinder engines?" For the US market, the answer is simple: "None." For the "gray market", the answer gets more interesting. I have found three or four Kubota tractors produced for non-US markets that were factory-equipped with turbocharged 4-cylinder engines:

- L4202 (1978-1985)- came equipped with the VT1502 engine, rated at 42hp, in contrast with the non-turbocharged V1500, V1501, or V1502 rated at about 35hp.
- L1-435 - equipped with the V1512-DI-TI-N engine(?), rated at 43hp
- L1-43/GL43 - equipped with a 4-cylinder turbocharged engine, unknown model

Here is an L4202 data plate:
View attachment 94705

One can search these model numbers in youtube, and find videos of them in operation, mostly in southeast Asia. I'm not sure if the V1512-DI-TI-N or V1512-DITC engines seen in these videos are factory-installed, or transplants. The V1512 engine was also used as a stationary powerplant (irrigation pumps, generators, etc.).

I have obtained a Parts List for the L3202 and L4202 tractors, and it includes part numbers for all engine parts for the non-turbocharged V1502 and the VT1502. What are the differences in these two engines? Besides the obvious (turbocharger and turbo compensator), they are:
- cylinder head casting
- piston and piston-ring assembly
- crankshaft
- connecting rod bearing [connecting rod part numbers are the same.

I am guessing that the crankshaft is different in that the rod journals are radiused, thus requiring a different connecting rod bearing. I have attempted to document the differences between the turbo and non-turbo cylinder head and piston. Here's what I have found:

V1502/1702/1902 Cylinder head casting (non-turbo):
View attachment 94708
VT1512 Cylinder head casting (turbo, 15345-03040):
View attachment 94710

It is easy to see the important difference here. The non-turbo head is an Indirect Injection head, with a spherical pre-chamber ported into the combustion chamber between the valves. The turbo head is a Direct Injection head. The injector nozzle protrudes through that chamfered hole between the valves.

Here are the two pistons:
View attachment 94714
The top piston is for V1512 (non-turbo) and the bottom piston is for the V1512-T. Notice that valve reliefs are missing from the turbo piston, and that it has a bowl in the top. The injector nozzle is centered in that bowl. Strangely, the injectors for the V1502 and the VT1502 in the parts list are apparently, the same (see below).

At this point, I want to introduce a very informative scientific review paper which discusses the engineering intricacies of turbocharged diesel engines. The title is: "A review of design considerations for light-duty diesel combustion systems" The two co-authors are at Lund University (Sweden) and Sandia National Labs (Livermore, CA).
Here is a link to the paper:

My favorite quote from the paper is:
"Thousands of man-years of effort have been expended in balancing multiple trade-offs as such basic parameters as compression ratio, bore-to-stroke ratio, and combustion chamber geometry are selected."

What I learned is that there are intricate design features of the piston bowl (into which the injector spray is placed) and its companion injector which have profound effects on the efficiency of combustion. Also, the piston height is greater in the turbocharged motor - it is what is known as a "quench" motor, where the piston approaches to within 0.6-0.8 mm of the cylinder head. This allows heat to more efficiently be transferred from the piston to the cylinder head and its water jacket. The space between the piston margins and the cylinder head is unavailable for combustion. The purpose of the bowl is to create "swirl" in the cylinder to improve mixing and combustion efficiency. The injector spray pattern must be carefully matched with the piston bowl.

Besides the piston and cylinder head design differences (turbo vs non-turbo), Kubota injector pumps are different for turbocharged engines. There is a turbo compensator, which adds additional fuel as boost increases to maintain the proper fuel-to-air ratio. I am not sure if the timing of Kubota injector pumps can be finely adjusted, but I know that it is infinitely adjustable with turbocharged Cummins motors. Timing should be retarded for turbo motors, because combustion is a more rapid event under the conditions of higher cylinder pressures and swirl.

Bottom line here is that simply slapping a turbo on a non-turbocharged engine ignores ALL of this...and is thus, a fool's errand. YMMV.
Yeah, it'll make a cool noise, but will it make more power?
Practically speaking, I see no opportunity to properly convert a non-turbo engine to turbo.

SO, then what???

Given that it would be very difficult or even impossible to get my hands on one of these gray market tractor models, and ignoring the challenges of parts support, what else can be considered?

I'm starting to think more and more about opportunities for engine swaps to turbocharge a non-turbocharged tractor model. It's attractive to consider the prospect of installing an entire engine to grab all the matched turbo-engine features at once.

What I'm looking to document now is the differences between the mounting systems at the bellhousing between readily available, domestic turbocharged Kubota engines, and the tractors I might want to install them in. So far, I've sifted through skid-steer loaders, to find the turbocharged 4-cylinder Kubota engines. Here's what I've found:

Bobcat 773 (1994-2001): V2003-T-E2B (46hp)
Bobcat S160 (2005-2013): V2003-M-DI-T (56 hp)
Bobcat S185 (2002-2013): V2003-M-DI-T (56 hp)
Bobcat S205 (2005-2013): V2403-M-DI-T (61 hp)
Bobcat S550,S570 (2013-present): V2403-M-DI-T (61 hp)
There are other Bobcats with larger turbocharged engines (V2607-T, V3307-T, V3800).

Yesterday, I looked at a Bobcat S185 and a S205 side-by-side. Interesting that, on the V2003 motor, the injector pump is on the right (radiator) end of the engine, and with the 2403, the injector pump is on the left (flywheel) end of the engine.

My thinking is that, if the bellhousing mounting pattern can be made to fit (modified or adapted), other things (like engine mounts, radiator location) are relatively easy.

-Paul
My MX6000 has a turbo.
 
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pigdoc

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G1800S L2500
Aug 19, 2022
275
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SE Pennsylvania
Thanks, Mike, and Wolfman,

The thought occurred to me that the 3-cylinder 1.6 DI engine in Mike's L2501 could have a bowl in the piston top, just like the turbo engines. If that is the case, except for a possible injection pump mismatch with a boosted engine, the combustion chamber should still be optimized, whether naturally aspirated or boosted. I guess that configuration (injection nozzle matched with a piston-top bowl) might be expected in ANY Direct Injection engine?

So maybe, I don't need a "turbo" motor per se, I need a Direct Injection engine to 'slap a turbo on'.

Mike, can you tell us what tweaks (if any) you made to the injection pump or timing when you boosted the engine? Can't wait to see your dyno numbers!

Wolfman, I wasn't aware that there were significant differences between the V1502 and the V1902, other than bore diameter. Your comment makes me presume there is more than one V1902 engine design. Just like the VT1502 has a different piston and cylinder head than a V1502, there are major design variations between V1902s? I'm still trying to get familiar with all the suffixes on engine model numbers.

On Monday, I asked about a creampuff L3350 (V1902) loader/backhoe with 1300 hours on it that the local museum owns. Maintenance manager told me that it's all they have for digging work and they're not looking to get rid of it, unless I want to replace it for them. Sour grapes: the thing has lived outside all its life and there is moss and lichens growing all over it. Looks like it's been horribly neglected.

tractordata is somewhat notorious for inaccurate or missing information on engines. The website shows the L3350 equipped with a "V1902-DA-A" engine. Is that a typo, or is that distinct from a V1902-DI?

Is there another (more accurate) list of engine numbers associated with obsolete Kubota tractor model numbers? And, I've really struggled to find engine specifications for obsolete Kubota engines. Any resources?

Thanks again, all,
-Paul
 
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JimmyJazz

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B2601
Aug 8, 2020
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Pittsburgh, Pa
Sometimes you need something to do. To "scratch an itch" so to speak. When I find myself "invested" as you are in something for which there is no real need I go to the library, take a long walk in the woods or try to write a song. The more channels your brain has the better I feel. If you are raising a family treat the offspring to new experiences to broaden their horizons. Chess, travel, skiing........ Good luck.
 
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GreensvilleJay

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just because you can, doesn't mean it's a good thing to do......

A great many moons ago , I was con-vinced to replace the 258-6 with 304-V8 in my '73 CJ-5. OK, <$1000 got the engine swap,exhaust,wiring,rad, etc....
2nd worse mistake I ever did.. sure 'quick as a bunny' off the line, great top end speed... LOUSY off road and plowing snow... 2 of my main purposes for having the JEEP.
 
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Rdrcr

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L2501 w/ S2T Turbo Kit = 35 PTO HP (Current), B2601 (Sold)
May 7, 2021
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^^^^^
I love that expression...."many moons ago"....I need to use it more!

Thanks, Mike, and Wolfman,

Mike, can you tell us what tweaks (if any) you made to the injection pump or timing when you boosted the engine? Can't wait to see your dyno numbers!

Thanks again, all,
-Paul
The L2501 and more specifically the D1703-M-DI-E4B engine is very unique in regards to performance enhancements, including Turbocharging. It's unique because the engine is severely detuned from the factory to meet Tier 4 emission standards. This same engine makes quite a bit more power in alternative applications. In the L2501, the D1703-M-DI-E4B engine, the injection pump timing has already been retarded, the fuel has been restricted and the maximum rpms have been limited. It's actually pretty well setup for Turbocharging right out of the gate. It really just requires installing the turbocharger and adding additional fuel. For my specific setup, I did not make any adjustments to the injection pump timing, just to the fuel delivery. There is a forum member with a L2501 that has also been turbocharged and he did advance the timing but, I would rather error on the side of safety. Plus, it simply isn't necessary, the tractor with the turbocharger is producing more than enough power as it is.

I'll be posting the dyno numbers next week.

Mike
 
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North Idaho Wolfman

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One other issue is that Power trains are designed for a set HP and Torque range for the stock motor that's installed.
You're also looking at 30 year old tractors that will already have worn parts, this could be problematic for a good running and reliable tractor.
 
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skeets

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All fun and games but is the outlay worth the return?
 

Rdrcr

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L2501 w/ S2T Turbo Kit = 35 PTO HP (Current), B2601 (Sold)
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^^^^
YES!!! :D

Mike
 

Oil pan 4

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L185 turbo
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Don't over think it. I have turbocharged non turbo IDI engines. They run great.
 
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War Eagle

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2012 B3000HSDC and Allis Chalmer 5020
Jan 15, 2017
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I bought a 44.2hp Kubota V1505 TE turbo charged engine with 138 hours on it. It was connected to a military generator and the generator went south. I was going to put it into my tractor that already has a non turbo V1505 but my health has taken a turn and now I don't have the energy or the will to tackle the project. So I will likely sell it to some one that could use it. I have a video of it running while connected to the generator. Since the military uses 24v you would need to change a few things to 12v.
1674927781293.png


1674927812825.png



1674927832860.png
 

mikester

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M59 TLB
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K builds nice machines but they are a little on the light side. If I need more HP then it's time to look at a bigger machine that can handle the job. I'm more interested in hydraulic GPM/pressures and pushing/pulling force, a few extra HP on a light frame won't make much of a difference at my elevation.
 

Oil pan 4

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L185 turbo
Sep 21, 2017
412
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I bought a 44.2hp Kubota V1505 TE turbo charged engine with 138 hours on it. It was connected to a military generator and the generator went south. I was going to put it into my tractor that already has a non turbo V1505 but my health has taken a turn and now I don't have the energy or the will to tackle the project. So I will likely sell it to some one that could use it. I have a video of it running while connected to the generator. Since the military uses 24v you would need to change a few things to 12v. View attachment 94771

View attachment 94772


View attachment 94773
A lot of them are 24v but I work on some that are 12v. The air force is going to start sht canning a bunch of Kubota 722 powered 2 lamp flood lights because parts for it are becoming obsolete. These things are between 10 and 22 years old and can have anywhere from hundreds of hours to tens of thousands of hours. Probably going to go for cheep.
 

North Idaho Wolfman

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One issue with trying to use a non AG motor in an AG use, is that a lot of them do not have the drive for the hydraulic pump, and it's not a bolt on part.
So while everything else bolts on and work, you end up dead in the water without any hydraulics.