Kubota l2501 throttle adjustment screw.

[Rdrett]

https://youtu.be/OAKMIvNsMCQ

My kubota l2501 has a throttle adjustment screw to increase the max engine RPM just like a small engine.

I posted a video showing the adjustment screw.

If I adjust this screw to allow the engine to rev higher will that have any kind of negative effects.

The l2501 has a d1703 engine that is rated at 25hp. If you search kubota d1703 engine it specs out at 30hp.

I believe the d1703 engine on the kubota l2501 is rated at 25hp at a lower rpm compared to other L series tractors.
If I increase the rpm I should get more HP?
On other engines the first thing I do is adjust that screw to allow the engine to rev higher.
Is it safe to do?

 

[motorhead]

I would never raise the top RPM unless you have specs on that engine that gives the max safe RPM. 2800 rpm seems to be the max. Specs say that it is 29.98hp at that speed.
I have a 2009 B3200 with the V1505 engine and it is rated at 32hp at 2700 rpm. I don't know what the difference in the two engines as your engine is a 1647 CC and my engine is 1498 cc. Mine is NON emission. That might make the difference.
What is the top RPM your engine will turn at now?

 

[North Idaho Wolfman]

Your asking for trouble.

Not all D1703's are built the same, there will be different internal components to make different HP at different RPM's.

Increasing the RPM's is not necessarily making more HP, it's just revving higher and thus shortening its life.

 

[dlundblad]

A guy on here with a landscaping business made the adjustment to get more engine speed and it seemed to have worked well for him.

The PTO gearing will always be the same so you won't be able to run the engine faster than 2000 RPM without exceeding 540 at the PTO.

While it's nice to know, I'm too much a chicken for this modification.

 

[North Idaho Wolfman]

A guy on here with a landscaping business made the adjustment to get more engine speed and it seemed to have worked well for him.

Who are you talking about?

 

[dlundblad]

Who are you talking about?

Can't remember his name. He had a B2650 originally, but later went with an L2501. He needed more speed to get the tractor out of deep holes with a full bucket.

 

[Rdrett]

A guy on here with a landscaping business made the adjustment to get more engine speed and it seemed to have worked well for him.

The PTO gearing will always be the same so you won't be able to run the engine faster than 2000 RPM without exceeding 540 at the PTO.

While it's nice to know, I'm too much a chicken for this modification.

The PTO speed is variable depending on load.
When I first started using my flail mower I would activate the PTO and increase the engine speed to get the PTO running at 540 and I would adjust my ground speed to keep the PTO spinning at 540.
If I increased my ground speed the PTO would fall below 540 rpm.
So I learned to increase the engine speed to max and adjust my ground speed to keep the PTO running at 540.
If I can increase the engine speed higher than it is now I can cut faster.

It is kind of hard to explain, hopefully you all understand.

 

[dlundblad]

The PTO speed is variable depending on load.
When I first started using my flail mower I would activate the PTO and increase the engine speed to get the PTO running at 540 and I would adjust my ground speed to keep the PTO spinning at 540.
If I increased my ground speed the PTO would fall below 540 rpm.
So I learned to increase the engine speed to max and adjust my ground speed to keep the PTO running at 540.
If I can increase the engine speed higher than it is now I can cut faster.

It is kind of hard to explain, hopefully you all understand.

If your pto/ engine speed decreases with an increase in ground speed, wouldn***8217;t that just be the engine lugging?

 

[Rdrett]

If your pto/ engine speed decreases with an increase in ground speed, wouldn***8217;t that just be the engine lugging?

Yes.
That is what I was trying to explain.
When I was cutting tall grass with my flail mower the engine would lug down decreasing the PTO speed.
I learned to run the tractor wide open and adjust my ground speed to keep the PTO spinning at 540.
When I hit tall grass and the engine started to lug down I would decrease my ground speed and when I hit grass that wasn’t as thick I would increase my ground speed to keep the PTO from spinning over 540.

When I first started cutting with my flail I would activate the PTO and rev the engine until my PTO hit 540 without any load on the PTO. Then I would cut at what ever speed necessary to keep the PTO spinning at 540.
That took twice as long to cut then the method I use now.
Run it wide open and lug the engine down to keep the PTO spinning at 540.

Hopefully my explanation is more clear and you understand what I am trying to say.

 

[D2Cat]

What I understand Rdrett to be saying is he sets the engine RPM near max, gets the PTO to 540, then adjust ground speed (to maintain the 540 PTO) and only changes gears as needed.

There's no lugging of engine in that scenario.

 

[Rdrett]

What I understand Rdrett to be saying is he sets the engine RPM near max, gets the PTO to 540, then adjust ground speed (to maintain the 540 PTO) and only changes gears as needed.

There's no lugging of engine in that scenario.

Exactly except I have a HST.
I will set throttle to wide open and maintain whatever ground speed is necessary to keep the pto spinning at 540rpm.

 

[North Idaho Wolfman]

Basically your flail mower is demanding more HP than your tractor can produce.

Increasing RPM to make up for the lack of the tractors available HP, will lead to heavy engine and transmission wear and damage over extended periods.

I would not be to surprised to hear you have an HST failure in a very short period of time.

 

[Rdrett]

Basically your flail mower is demanding more HP than your tractor can produce.

Increasing RPM to make up for the lack of the tractors available HP, will lead to heavy engine and transmission wear and damage over extended periods.

I would not be to surprised to hear you have an HST failure in a very short period of time.

The tractor has plenty enough power to run the flail mower.
The question is how fast I can get it done.
I purchased a heavy duty flail mower that is rated up to 3 inch’s and the tractor has plenty of torque to chew through stuff 3 inches thick.
I have never stalled the mower from lack of power.

Think of it like a regular lawn mower.

You start the engine, max throttle and cut the grass.
If the grass gets to thick you have to slow down as to not bog down the engine and stall the machine.

Same concept I am using during mowing with my tractor and flail.

Now if you have a regular law mower with a tiny 12hp motor and you try and cut tall grass as slow as you possibly can and still stall the motor then you need more HP.

I don’t have that problem with my tractor.
I can go at a crawl and chew up 3 inch material and not even come close to stalling the engine. It has plenty of power.

The engine in the kubota is tuned was down that’s why it doesn’t rev as high as a kubota l3301.

 

[North Idaho Wolfman]

The engine in the kubota is tuned was down that***8217;s why it doesn***8217;t rev as high as a kubota l3301.

I'll stop you right there, that's a big NEGATIVE!

The l2501 and the L3301 have different engines period.

You can not squarely compare the 1.6L L2501's mechanical fuel injection engine to a 1.8L L3301 electronic fuel injection engine.

Saying, "Well i'm just going to turn up the RPM limit set screw to match what the L3301's RPM is and I'll have the same thing" is flat out wrong!
It's not the same HP curve or output, you do not increase HP by simply turning up RPM!

If your mower is bogging down your tractor, It doesn't have enough HP, period.
I didn't say it didn't have enough torque, that a whole different discussion, heck you can pull a semi with a pedal tricycle with the right gearing, doesn't make it right or efficient.

 

[SidecarFlip]

Interesting thread. All my kubota's that I've owned over the years including both of them I now own, have all had the throttle stop screws safety wired in place and I've never 'adjusted" any of them. I figure they were safety wired in place for a good reason.

 

[Rdrett]

I'll stop you right there, that's a big NEGATIVE!

The l2501 and the L3301 have different engines period.

You can not squarely compare the 1.6L L2501's mechanical fuel injection engine to a 1.8L L3301 electronic fuel injection engine.

Saying, "Well i'm just going to turn up the RPM limit set screw to match what the L3301's RPM is and I'll have the same thing" is flat out wrong!
It's not the same HP curve or output, you do not increase HP by simply turning up RPM!

If your mower is bogging down your tractor, It doesn't have enough HP, period.
I didn't say it didn't have enough torque, that a whole different discussion, heck you can pull a semi with a pedal tricycle with the right gearing, doesn't make it right or efficient.

The mower doesn’t bog the engine down. I let off the HST pedal and slow down before the engine bogs down. That is my whole point.

It feels like I am mowing with throttle set to 3/4.
When I first got the tractor I kept finding myself yanking on the throttle lever to try and increase the rpms.
The tractor just doesn’t rev very high.
The throttle stop screw has an unbelievable amount of adjustment and the engine doesn’t rev very high.

I was hoping for someone with some first hand experience on the throttle stop.
They put a throttle stop adjustment on the tractor for a reason. (To limit the max rpms).

I do plan on making this adjustment I was just looking for any advice before I do.

I will post the results when I am done. I wish I had a pto dyno to get some accurate data.

 

[North Idaho Wolfman]

Can I please change the thread title to:

How to Blow it up!

Because that's all I'm getting out of this thread!

None of your points make any sense!

The RPM setpoint is the set point, RPM max is RPM max, I doesn't say in the manual or anywhere, if you run out of RPM's because your over working your tractor turn it up some more to compensate!

 

[Rdrett]

Can I please change the thread title to:

How to Blow it up!

Because that's all I'm getting out of this thread!

None of your points make any sense!

The RPM setpoint is the set point, RPM max is RPM max, I doesn't say in the manual or anywhere, if you run out of RPM's because your over working your tractor turn it up some more to compensate!

The rpm is not a set point.
It has an adjustment screw to set max engine rpm.
If I turn it one way it will not let the throttle lever go as far reducing the engine rpm. If I turn it the other way it will let the throttle lever go farther giving the engine more gas, increasing the rpm.

All work that I have done so far hasn’t hurt anything on my kubota.
I only use it a couple times a year to mow with and that is the only load I put on the tractor. 90% of its life has been at idle.

But if I did damage it who cares? It’s mine and I don’t.

The kuota l2501 has a very low max rpm compared to almost any tractors I have used. That is why I tried yanking on the lever to increase the rpms when I first got it.

 

[Rdrett]

Guys I know this is a hard question to answer but my main concern was:

Hydraulic pump capable of running at higher rpms?
To much hydraulic pressure damaging thing but the pressure relief valves should protect over pressure issues.

I don’t know if the hydraulic pump installed on the l2501 has a max rpm spec.

I already know for a fact I can adjust the max engine rpms just wanted to know if that would effect any other systems on the tractor.

The reason I originally questioned this is because I felt the engine didn’t rev as high as it should and after doing some research on kubota engines I found that the kubota l2501 engine reved at a lower rpm than other kubota d1703 engines.
I also found that the d1703 engine is rated at 30 hp at a higher engine rpm.
I thought it was odd that kubota put a 30hp engine in a 25hp tractor and reduced the max engine rpm and called it 25hp.

 

[dlundblad]

If you can find out if the L2501 has the same HST/ pump as larger L***8217;s then that would give you your answer.