Kubota l2501 throttle adjustment screw.

[North Idaho Wolfman]

You really don't get it do you????

Your tractor is rated at PTO Speed 540 @ 2106 RPM.
It's not a variable, it's fixed, more engine rpm = more PTO rpm.

You turning up the max RPMs of the engine which in turn, turns up the PTO RPMs, yea bad things are going to happen.

You turn up the engine rpms and the hydrostat now has to work with those Higher RPMs yea bad things are going to happen

You turn up the RPMs and now the hydraulic pump is spinning faster heating the fluid in the system up, yea bad thing are going to happen.

You turn up the RPMs on an engine that was designed for a MAX of 2200 RPM's Yea bad things are going to happen.

Yea they may not happen immediately, but they will most likely happen to the poor sucker that gets the tractor after your done with it.

 

[North Idaho Wolfman]

If you can find out if the L2501 has the same HST/ pump as larger L's then that would give you your answer.

No it won't give you the answer...
Just because it has the same HST unit does not mean Squat!

 

[North Idaho Wolfman]

It's stupid and dangerous to turn up a rated engines RPMs and it's PTO speed just because you really need a bigger tractor that will actually handle the equipment your running!

 

[BAP]

So let me get this right, you are basically on here asking for verification that you can over rev your engine to get a smidgen more Umph out of your tractor that you bought and really is not quite big enough, and want someone to say that you can do so, so that when the motor prematurely has problems you can point your finger and say, the people on Orange Tractor Talks said I could do it. It is not my fault Kubota, I want you to buy me a new motor. If you are unhappy with the performance, then the best solution is buy bigger or go slower. We all know it is your tractor and you can do what you want, but why do you keep trying to get people to support you? If you are that confident with what you want to do, then do it and see what happens.

 

[Blondie70]

Try going up 100 RPM at a time and check out the performance.

 

[SidecarFlip]

It's stupid and dangerous to turn up a rated engines RPMs and it's PTO speed just because you really need a bigger tractor that will actually handle the equipment your running!

A little story about me....

First off, like I said, I never fool with any settings on an engine, especially those that are safety wired....

Anyway, back when I owned the 5030 HSTC prior to my M's, I was just getting into hay and bought a 4x4 round baler (NH). I knew going in that the 5030's rated PTO output was marginal to run the baler but I had to give it a shot anyway because the 5030 ran everything else just fine and I liked the tractor just fine. So, I'm out in the field and start a bale and as the bale grows, the engine rpm's start dropping because the 5030 wasn't making enough PTO horsepower to keep up so I opened the throttle up to the stop and it kind of worked, sort of, but I knew I wasn't doing the engine any favors so I trundled down to my dealer traded it in and bought the 105X off the lot and then ordered the M9 a few weeks later.

I could see that the 5030 wasn't going to last doing that so I traded up. In my case, way up but the bottom line is neither the 105 nor the M9 is taxed at all even with my new 4x6 round baler.

My personal opinion is, you need to upsize. You cannot get 5 gallons of water from a gallon jug.

It's your tractor and you can do whatever you want to but when it pukes you have no one to blame but yourself.... and it will puke at some point.

 

[RCW]

I'm with Wolfman and BAP....

Damned fool if you do that in my book.

If you have problems down the road, nobody to blame but yourself.

Your tractor, do as you please... undeniable fact and I respect that.

Godspeed, my friend.

Sent from my QTASUN1 using Tapatalk

 

[dlundblad]

No it won't give you the answer...
Just because it has the same HST unit does not mean Squat!

What’s the difference between the HST running at a higher RPM on this vs. say the 4701 assuming it is the same unit?

Keep in mind, I’m just talking about the HST and not the PTO speed.

 

[Rdrett]

It's stupid and dangerous to turn up a rated engines RPMs and it's PTO speed just because you really need a bigger tractor that will actually handle the equipment your running!

I don’t need a bigger tractor. I actually need a smaller tractor.

It is obvious that people here don’t have enough basic knowledge of the topic or are just being snobs.

Very few people have brought up any good points, all they have done was whine like a baby, don’t do that I “think” that’s not a good ideal. I am “guessing” your going to blow up the engine. I am surprised you haven’t “already” blew up your engine on you tractor that only has 200 hours on it even tho you haven’t even made the adjustment yet. You already “damaged” the engine just by thinking about making that adjustment.

I thought I would post this question here and someone who had enough technical knowledge would chime in or someone who has actually done the modification.
It is obviously that nobody here has enough technical knowledge to answer the question.
Everyone here goes off the “feelings” instead of knowledge.
-“I have a feeling you are going to blow the engine”.
-“I have a feeling you already damaged your engine just thinking about turning that screw”.
-“I have a feeling you need a bigger tractor”.

This tread is dead to me and I think I will go ask the question somewhere else where people seem to have more technical knowledge and go off of experience instead of their feelings.

I was hoping someone would respond.
-Yea I have a d1703 engine in different piece of machinery at it revs at ___rpm.
-Yea I have made this adjustment and have first hand knowledge.
-You do this and maybe it will effect this.
-You do this and it shouldn’t effect this because of this.

Instead I have people who respond with no technical knowledge one who claims that I have already damaged my tractor just thinking about turning the screw.

It now is very obvious that I asked the wrong question in the wrong forum.
That poor kubota tractor. I LOVE kubota SO much and that idiot guy rdrett is going to kill that poor kubota by turning up the max rpm a couple hundred rpm.

After doing my research I am postive that kubota put 30hp engine in the l2501 and “tuned” it down to 25hp.
I am pretty sure by limiting the max rpms and changing the pto gearing to spin the pto 540 at a lower rpm.
Other machines with a d1703 engine rev higher than a l2501 and are rated at 29.5-30.5hp depending on machine.
It doesn’t make sense to me that kubota would use different different parts for the d1703 engine on the l2501 compared to other d1703 engines.

Fact is kubota put a 30hp engine in the kubota l2501 and “tuned” it down to 25hp. How they did that was my main question. The only way I can think of them tuning down a MECHANICAL engine like the d1703 would be with manual adjustment. This engine is NOT computer controlled.

 

[Rdrett]

What’s the difference between the HST running at a higher RPM on this vs. say the 4701 assuming it is the same unit?

Keep in mind, I’m just talking about the HST and not the PTO speed.

It would not make a difference if the HST pump is the same exact pump running at higher rpms on other machines.

To many kubota lovers here go off their feelings instead of knowledge.
Rdrett destroyed that poor kubota just thinking about turning that screw.

 

[Rdrett]

So let me get this right, you are basically on here asking for verification that you can over rev your engine to get a smidgen more Umph out of your tractor that you bought and really is not quite big enough, and want someone to say that you can do so, so that when the motor prematurely has problems you can point your finger and say, the people on Orange Tractor Talks said I could do it. It is not my fault Kubota, I want you to buy me a new motor. If you are unhappy with the performance, then the best solution is buy bigger or go slower. We all know it is your tractor and you can do what you want, but why do you keep trying to get people to support you? If you are that confident with what you want to do, then do it and see what happens.

I didn’t what anyone to “support” me.
I wanted people with actually knowledge to chime in instead of people going off their “feelings”.

I am very confident in turning up the max rpm on the l2501 to match the max rpm on other d1703 engines safely without damaging the d1703 engine. My main concern was other systems on the tractor.

 

[leoric]

I won't tell you what to do but in general taking an engine and reducing the RPMs changes the spot you'll end up on the torque/hp curves. I doubt that Kubota would be able to simply turn less RPM's and still achieve a desirable cross section of those two curves. There are a lot of other factors that go into the output of a motor than simply rpms. Fuel supply, air supply, timing, and end consumers (hydraulic pump size, alternator, etc). I'm betting you're right that the motor has been retarded down to 25hp but I'd be more worried about the other end components that aren't only the engine. You might say you need a smaller framed tractor such as a b, but truth is you're taxing the engine and if you want to go at max speed while maintaining you're pto output you do need more horsepower. Which would mean a bigger tractor (HP wise) could be a B3350 could be an L.

Can you up the boost on a stock duramax? Yeah, but eventually you'll break something. Can you turn up your RPMs on your tractor? Yeah but eventually you'll break something. That is all the guys here are saying and I'm in agreement. Trading up to a bigger tractor HP will cost $$ but fixing things costs $$ so where do you want to put your money?

 

[Rdrett]

I won't tell you what to do but in general taking an engine and reducing the RPMs changes the spot you'll end up on the torque/hp curves. I doubt that Kubota would be able to simply turn less RPM's and still achieve a desirable cross section of those two curves. There are a lot of other factors that go into the output of a motor than simply rpms. Fuel supply, air supply, timing, and end consumers (hydraulic pump size, alternator, etc). I'm betting you're right that the motor has been retarded down to 25hp but I'd be more worried about the other end components that aren't only the engine. You might say you need a smaller framed tractor such as a b, but truth is you're taxing the engine and if you want to go at max speed while maintaining you're pto output you do need more horsepower. Which would mean a bigger tractor (HP wise) could be a B3350 could be an L.

Can you up the boost on a stock duramax? Yeah, but eventually you'll break something. Can you turn up your RPMs on your tractor? Yeah but eventually you'll break something. That is all the guys here are saying and I'm in agreement. Trading up to a bigger tractor HP will cost $$ but fixing things costs $$ so where do you want to put your money?

Thanks for the helpful post instead of the bashing.
You are correct.
-fuel supply. The l2501 has the same fuel injection pump as all other d1703 engines.
-Air supply. The l2501 has the same air supply as all other d1703 engines.
-timing. Not sure what part to look up for that.

I have checked a lot of other part numbers as well and from what I can find the l2501 d1703 engine used the same parts as any other d1703 engine.

I am not to worried about blowing up the engine prematurely. I want to turbo the engine anyway and I need to change the pistons to do that.

 

[SidecarFlip]

Thanks for the helpful post instead of the bashing.
You are correct.
-fuel supply. The l2501 has the same fuel injection pump as all other d1703 engines.
-Air supply. The l2501 has the same air supply as all other d1703 engines.
-timing. Not sure what part to look up for that.

I have checked a lot of other part numbers as well and from what I can find the l2501 d1703 engine used the same parts as any other d1703 engine.

I am not to worried about blowing up the engine prematurely. I want to turbo the engine anyway and I need to change the pistons to do that.

A bit more than just the pistons....

Why not trade it in and just get a bigger unit. I don't follow your thinking at ll.

 

[Rdrett]

A bit more than just the pistons....

Why not trade it in and just get a bigger unit. I don't follow your thinking at ll.

I realize that to turbo the engine it needs more than pistons to do that but I was saying that I need to tear down the engine to replace the pistons when I go to turbo it. Which will require a complete engine disassembled.

I don’t want to trade it in for a bigger unit because.
-I don’t need a bigger tractor. I actually need a smaller tractor possibly with more hp.
-The tractor I already paid for has deprecated about $5,000. Why would I buy another brand new tractor that will deprecate another $5,000 after a couple hundred hours?
-Why wouldn’t I turn the 30hp motor that kubota tuned down to 25hp and make it 30hp?

 

[SRG]

He obviously understands that there is a potential for failure of some thing, at some time. He's stated he has done his homework/research on what information is available, on the particular engine, and it's twins, that are in different platforms. I'd think most people that modify internal combustion engines, usually have a good grasp of this. I don't really understand what the problem is, in helping the guy get an answer. It's his to do with as he wants.

OP, I hear ya loud and clear. I have been in the same boat, as the particular engine in my machine is also used in alot of other platforms (tractors, generators, excavators, skid steers, etc. etc.), with different ratings at different RPM's. Mine in particular (870), is rated 28HP @ 2800rpm fast idle, 540 PTO 25hp rated @ 2600rpm. The exact same engine in a slightly older and smaller machine (955), is rated 33hp @ 3400rpm fast idle, 540 PTO 27hp rated @ 3200rpm. With the same bore and stroke, same cylinder head, same hydraulic pumps, same injector pumps. Only thing i haven't been able to find information on, is camshaft specs related to the valve events. That info would have the biggest effect on a particular engines ratings (RPM, TQ/HP, area under the curve), the cam is the brain of the engine. I've come across tolerances for the camshaft lobe sizes, and what is acceptable wear specs for the cam lobes, but that's all I can find.
I'd think if you can find camshaft specs, you'd be able to determine alot of info from that, all else being equal, as you've been finding. I don't think that is an easy task, short of removing the camshaft(s) of the same engine, from different platforms, and having them spec'd by a machine shop.
Nobody "hotrods" these things, so most pertinent info, just isn't out there for public consumption.

3TN84

 

[Rdrett]

SRG.
Thanks for the reply. I forgot to check the camshaft. I will look into that.

Here are some Information I found online about the d1703 engine.

KUBOTA
D1703 KUBOTA

HORSEPOWER : 17.2-30 HP SPEED : 1500-2800 RPMTYPE : DIESEL
Horsepower: 30
Low Noise
The Kubota D1703 is a vertical, water-cooled, 4-cycle diesel engine with a capacity of 30HP at 2800RPM. Featuring a built-in solenoid, low fan position and single side serviceability, the Kubota D1703 offers powerful performance, exceptional reliability and a long service life to meet almost any application.

My kubota l2501 max rpm is 2,400 rpm. Which is very low and why I kept yanking on the throttle lever when I first got it.
The d1703 engine is rated to run between 1500-2800 rpm.
I am positive I can turn the engine up to 2,800 rpm without any negative effects on the engine.
Just because I turn it up to 2,800 rpm doesn***8217;t mean I am going to run it 100% of the time at 2,800.
The only time I will run it up to 2,800 rpm is when I travel on the road or need to dig myself out of a hole.

I will most likely set max rpm at 2,600 at test from there.

 

[SRG]

Camshaft. Intake open and close, exhaust open and close, intake center line, overlap, lobe separation angle, lobe ramp profiles, valve lift, etc..

Crankshaft only matters, if the stroke is different, which I doubt. if it was I'd think the engine designation would be different as well, since it would alter displacement.

 

[Rdrett]

Camshaft. Intake open and close, exhaust open and close, intake center line, overlap, lobe separation angle, lobe ramp profiles, valve lift, etc..

Crankshaft only matters, if the stroke is different, which I doubt. if it was I'd think the engine designation would be different as well, since it would alter displacement.

Camshaft is what I meant.
I already checked the crankshaft and it is the same part number as all other d1703’s.

I will see if I can check part numbers for the cam, heads, valves.

 

[SRG]

Camshaft is what I meant.
I already checked the crankshaft and it is the same part number as all other d1703’s.

I will see if I can check part numbers for the cam, heads, valves.

Keep in mind, that different part numbers may not necessarily mean different cam profiles, but could just be a different cam gear bolt pattern or something mundane like that, which would have no effect on the output.