My 863 bobcat brush mower loses power in heavy grass. I rebuilt the pump on brush cutter. I hooked up auger and the guger turns slow like hydraulic flow is low. what should I ck.

Probably the same as a car and needs a sealed system for Pump, Emissions and Evap.

https://www.google.com/search?q=bobcat+863+service+manual+pdf+free

Fixya isn't really a heavy plant site. There must be better forums.

..

The Bobcat 863 is a skid steer loader model manufactured by Bobcat Company, a renowned manufacturer of construction equipment. The 863 model was produced from 1996 to 2003 and was part of the C-Series lineup. Here are some key details about the Bobcat 863:

1. Engine: The Bobcat 863 is powered by a diesel engine. The 863 was initially equipped with a Deutz BF4M1011F engine, which is a four-cylinder, turbocharged engine. Later models may have variations in engine specifications.
2. Operating Capacity: The operating capacity of the Bobcat 863 depends on the specific configuration and attachments used. However, it typically falls within the range of approximately 1,500 to 2,000 pounds (680 to 907 kilograms).
3. Hydraulic System: The 863 features a hydraulic system that powers the loader arms and attachments. It has auxiliary hydraulic ports for connecting various hydraulic-powered attachments, such as buckets, forks, grapples, and hydraulic hammers.
4. Controls: The 863 is equipped with joystick controls that allow the operator to maneuver the machine with precision. These controls enable the operator to manipulate the loader arms, drive functions, and auxiliary hydraulics.
5. Attachments: The Bobcat 863 is compatible with a wide range of attachments, making it versatile for various applications. Common attachments include buckets for general-purpose loading, forks for material handling, augers for digging, and sweepers for cleaning.
6. Safety Features: Like all Bobcat equipment, the 863 is designed with safety in mind. It features safety interlock systems to prevent accidental operation and rollover protection structures (ROPS) to protect the operator in the event of a tip-over.
7. Maintenance: Regular maintenance is essential to keep the Bobcat 863 operating efficiently. This includes routine checks of fluid levels, engine oil, hydraulic system, filters, and tire pressure.

if the hydraulic oil is from the auger head then the machine will fill and bleed out the air
the hydraulic oil would have been in the hydraulic motor that drives the auger

basically there are 2 points of control
1---is the control valve for that side which may not be opening the system
2--- the drive motor for that side which may be passing excessive oil and not turning
for the lift action to be slow indicates excessive pressure leakage in that circuit
early units had lever action to the control valves where as later units use electronic controls from joysticks to operate the valves
If this is your type of machine, I would be looking at faulty electronic control mechanisms or corroded wires and contacts

Bobcat 863 863H Service Repair Manuals - YouTube

? 3:17
www.youtube.com/watch?v=Hsp-NAdM4Sg
Oct 30, 2010 - Uploaded by DiyRepairManuals
Bobcat 863 863H, Service Manual, Repair Manual.

Bobcat 753 Service Manual

How to Replace Hydraulic Hose

check fuel filter and pump pressure starving for gas

turn it upside down clean all the dried grass away from the holes around cutter shaft, apply a few drops of 3 in 1 or similar oil to shaft
bearing. Clean all dried grass from holes around top of motor casing
re try machine if it is not faster than before motor brushes are worn
and its time to buy a new one

with out a load on it and running dosen't mean the pump is good not as much pressure is needed without a load