Brush Cutter for Jinma

[RonMar]

pto is set at 540 with the rpm around 1300/1500.

g0rd0, like Greg said, you need to have the tach up in the green arc around 2300 RPM to get the rated 540 RPM at the PTO shaft. Especially when cutting grass, you need a certain blade tip speed in order to cleanly sever the grass stalks. The gearbox on the cutter is designed to give the necessary blade speed(around 13,000 FT/MIN) when 540 RPM is applied from the PTO. Less RPM and it won't cut right. You use your gear selection to determine the speed you travel over the ground, not the throttle, that stays at full all the time you are mowing. The governor top end setting will limit the RPM to no higher than the green arc, even with the throttle lever pushed as far forward as it will go.

I slowly let out the clutch at about 1000 RPM to get the blades spinning. As soon as the first stage clutch(pto section) is fully engaged, I smoothly push the throttle lever as far forward as it will go and leave it there. The remainder of my mowing session uses just half of the clutch pedal travel to control the second stage of the clutch(drivetrain clutch) for shifting. The only time I come out of full throttle is when I am done cutting, or the temp starts to creep up because the filter screen in front of the radiator is full of debris and blocking airflow and I have to stop and clean the screen...

Force = mass X acceleration. The real power of the brushhog, especially when shredding brush and sapplings/small trees is in the energy stored in the blades at their designed RPM. At 1400 engine RPM, you are only getting half the performance out of your mower, and less than 1/2 the available HP out of your engine. Lugging a diesel engine is not healthy for it. Does your engine bog down when the material being cut gets thick? I would guess it does. The only time mine bogs down is when it gets into something like a rootwad of one of the larger sapplings/trees I have just pushed over that gets uprooted and tangled in the blades Simple brush and grass, it dosn't change speed very much at all...

With sharp blades, my hog delivers a pretty decent cut on grass, even when it is a little wet... Push your throttle all the way forward, i think you will be pleasantly surprised at how the cutter performs...

 

[Diamondpilot]

The fenceline concern is common, I understand that. But you might be surprised if you actually measure your rear track. A JM254 with original rims/tires has an adjustable rear track between 1070 and 1250 millimeters. That means the widest possible positioning is 49.2 inches.

//greg//

Mine has standard R1 tires and wheels, 284 but the same thing, and I can guarantee you its wider than that. Yes, my wheels are flipped but I would guess its 5'5". Reason I say that is I have my 72" Caroni finish mower on it right now and there is maybe 4" on each side. Also in the winter I have a 6' and 7' grader blade for the 3 point. With the 6' it barely covers the wheel track strait and forget about it with the blade angled.

I am in Fresno on a flight today but will measure and confirm when I get home. I may be way off here.

Chris

 

[Diamondpilot]

Not sure where you got your info Greg but my rears are 61 wide and the fronts are 57

Chris.

 

[Diamondpilot]

Last pic is my tractor, 60" bucket, and my 72" Caroni finish mower.

Chris.

 

[greg_g]

Not sure where you got your info

Right straight out of the owner's manual Chris.
JM254/284;
wheelbase; 1050mm
front track; 900 mm or 950mm on reversed rims
rear track; four position adjustable from 1070mm to 1250mm

Don't know what you may have done since purchasing yours, but both my JM254s conformed exactly to those measurements above. I had mine set "wide", and a 60"' bush hog extended several inches past both rear tires. Mowing up close to a fenceline was no problem.

//greg//

 

[Diamondpilot]

Right straight out of the owner's manual Chris.
JM254/284;
wheelbase; 1050mm
front track; 900 mm or 950mm on reversed rims
rear track; four position adjustable from 1070mm to 1250mm

Don't know what you may have done since purchasing yours, but both my JM254s conformed exactly to those measurements above. I had mine set "wide", and a 60"' bush hog extended several inches past both rear tires. Mowing up close to a fenceline was no problem.

//greg//

Imagine that, the manual is wrong. I know as a current owner they are much wide than you say.

I have done nothing other than set it to wide stance. There must be some changes since you had yours but you can clearly see my 2003 Jinma 284 is every bit of 5' wide as it sets.

You can clearly see that there is no more than 4-5" on each side of my rear tires and my 6' (72") Caroni Finish Mower. You can also see that the 5' wide bucket on my FEL is the same width as my rears and my fronts are slightly narrower.

Chris

 

[Diamondpilot]

Here is a pic of my fronts.

Chris

 

[greg_g]

I may have partially figured this out. The Chinglish manual - as you know - can be subject to more than one interpretation. As such, I wasn't too accurate with those numbers I extracted originally. Here is the corrected version:
Wheelbase; 1645
Front; 920 or 1000
Rear; 1000 to 1300
But your measurements are all outside to outside (tire). The Jinma numbers I cite are center to center (rim). So your tractor may have wider rims/tires than mine (I had the skinny rice tires). And given that I could trim fencelines just fine with a 60" mower, I clearly didn't have my wheels set as wide as yours either.

Moral of the story is; size your mower selection to your own tractor and conditions.

//greg//

 

[Diamondpilot]

My tires are:

Fronts=6.00x16
Rears=9.5x24

Chris

 

[Diamondpilot]

On my way to bush hog with my 5' (60") Ford cutter.

Cutter is actually 64 wide.

Chris