THE ACREAGE EQUIPMENT FIELD GUIDE
Gross or net engine horsepower: SAE J1995, SAE J1349 and engine-rated attachments
Some tractor makers print two engine figures: gross power under SAE J1995 and net power under SAE J1349. The net figure is lower. When an attachment is rated in engine horsepower without naming a standard, a tractor near the line can pass on one figure and fail on the other. Kubota’s MX specification sheet shows both, and the gap decides several screens.
By Acreage Equipment · Reviewed November 8, 2026 · Specification research, not a field test
THE DECISION IN NUMBERS
Kubota MX gross and net engine power against engine-rated limits
Tractor values quoted from Kubota’s MX specification sheet (May 2025), reviewed November 8, 2026. Attachment limits from retained product evidence reviewed November 7: Wallenstein BX72S 50 engine hp minimum, BX52S 55 maximum; neither names gross or net.
Scroll the table sideways on smaller screens.
| Tractor | Gross / net / PTO hp | BX72S (50 minimum) | BX52S (55 maximum) |
|---|---|---|---|
| MX4900 gear | 50.3 / 47.7 / 41.3 | Gross +0.3; net −2.3 | Inside on both |
| MX4900 HST | 51.8 / 48.5 / 41.3 | Gross +1.8; net −1.5 | Inside on both |
| MX5400 gear | 55.5 / 53.0 / 46.5 | Inside on both | Gross 0.5 over; net inside |
| MX5400 HST | 57.0 / 53.8 / 46.5 | Inside on both | Gross 2.0 over; net inside |
| MX6000 HST | 63.4 / 59.5 / 51.8 | Inside on both | Over on both |
Sources for this decision table (3)
- Kubota MX specification sheet (PDF modified May 14, 2025) ↗Printed pp16–17: gross SAE J1995 and net SAE J1349 power, PTO power, Category I & II, lift at 24 in., weights
- Wallenstein BX72S official U.S. page ↗Engine HP Range; Mounting System (Cat I and II); Total Weight; Discharge Chute Height
- Wallenstein BX52S official U.S. page ↗Engine HP Range; Total Weight
What the two standards measure
SAE J1995 gross power is measured with the engine stripped of some accessories that it carries in the tractor. SAE J1349 net power is measured with the engine as installed, so it is lower. Neither is PTO power, which is measured at the PTO shaft after the transmission. Kubota’s MX sheet lists all three; many catalogs print only the gross figure, marked with an asterisk.
How large the gap is
On Kubota’s MX sheet the gross-to-net gap is 2.6 hp (MX4900 gear), 3.3 (MX4900 HST), 2.5 (MX5400 gear), 3.2 (MX5400 HST) and 3.9 (MX6000). That is enough to cross an attachment’s minimum or maximum: the MX4900’s gross figures clear Wallenstein BX72S’s 50-hp minimum and its net figures do not. The MX5400 HST’s 57 gross hp is over BX52S’s 55-hp maximum; its 53.8 net is under it.
What attachment makers say
Wallenstein labels its chipper ranges Engine HP. Farmry’s WCAP5 manual says Engine HP Range. Neither names gross or net in the retained sources. Land Pride, Farmry’s LFS and TMG give tractor hp without naming engine or PTO at all. When a maker gives only “engine hp”, ask which standard it means before relying on a margin smaller than the gross-to-net gap.
Using the right tractor figure
Use the figure the attachment maker specifies. If the maker cannot say, the net figure is the conservative choice for a minimum and the gross figure for a maximum. A tractor that passes on both is inside either way. Where a tractor maker publishes only gross power, the net figure is unknown; do not estimate it.
Take these questions with you.
- Does my tractor’s spec sheet list gross (SAE J1995), net (SAE J1349) or both?
- Which engine standard does the attachment maker use for its range?
- Is my tractor inside the range on both figures, or only one?
- If only one, will the maker confirm the pairing in writing?
Keep these questions with your exact tractor and attachment details.
Use these questions in my seller briefFOLLOW THE NUMBERS
Sources & documentation
Research record reviewed November 8, 2026. Confirm the current manual and the exact revision supplied with your machine.
- Kubota MX specification sheet (PDF modified May 14, 2025)Printed pp16–17: gross SAE J1995 and net SAE J1349 power, PTO power, Category I & II, lift at 24 in., weights
- Kubota TC860-1971-9 operator manual, MX4900/MX5400/MX6000 (©2019, hosted by Garton)Printed pp23–24 MX4900 specifications; printed p31 implement limitations (flail 72 in. / 1,100 lb)
- Wallenstein BX72S official U.S. pageEngine HP Range; Mounting System (Cat I and II); Total Weight; Discharge Chute Height
- Wallenstein BX52S official U.S. pageEngine HP Range; Total Weight
- Farmry WCAP5 operator manual, Rev 1.5Printed p19: Engine HP Range 15–45, 5 × 9-in. opening; p20: 412 lb with PTO shaft
- Farmry official product specifications
- Wallenstein BX52S support — currently linked operator, setup and shaft documents
- BX-S operator manual Z97085_En, Rev Jan-2025 — pp14,18–22,28,30,40
- PTO shaft installation Z97844_En, Rev Aug-2024 — p6 sizing with a quick hitch attached
- BX-S setup instructions Z97085_SI, Rev Feb-2019 — assembly and shipment handling
- BX72S official support page — current operator/setup documents
- Land Pride FM25 current North American family and model listing
- Official FM25 public catalog response — active models, gallery and linked documents
- FM25 operator manual 333-138M, printed 7/1/24 — requirements pp14–20, options pp15,30,33, specifications p39
- Official FM25 brochure — printed p12 model table
