Small Engines (Lawn Mowers, etc.): toro lawn tractor, hydrostatic systems, hydrostatic system

Question
i just picked up a '97 toro wheelhorse 16-44 mo. no. 71196. engine runs great, cuts great but there seems to be a problem with the hydrstatic tranny.  it goes very slow.  i replaced the drive belt, still very slow?????  where else may i have a problem???

Answer
todd
Check for thr following problems

Engine speed low
Control linkage bent or out of adjustment
Brake setting incorrect
Drive belt slipping or pulley damaged
Oil level low or contaminated oil
Excessive loading
Bypass assembly sticking
Air trapped in hydraulic system

Soulitions to try to fix

Adjust to correct setting
Repair or replace linkage
Adjust brake to proper setting
Repair or replace drive belt or pulley
Fill to proper level or change oil
Reduce vehicle loading
Repair or replace valve or linkage
Purge hydraulic system

How to purge the system

Due to the effects air has on efficiency in
hydrostatic drive applications, it is critical that it
be purged from the system.
These purge procedures should be implemented
any time a hydrostatic system has
been opened to facilitate maintenance or any
additional oil has been added to the system.
Air creates inefficiency because its compression
and expansion rate is higher than that of
the oil approved for use in hydrostatic drive
systems.
The resulting symptoms in hydrostatic systems
may be:
1. Noisy operation.
2. Lack of power or drive after short term
operation.
3. High operation temperature and excessive
expansion of oil.
Before starting, make sure the transaxle/
transmission is at the proper oil level. If it is
not, fill to the specifications in your manual
The following procedures should be performed
with the vehicle drive wheels off the ground,
then repeated under normal operating conditions.
1. With the bypass valve open and the engine
running, slowly move the directional control
in both forward and reverse directions
(5 to 6 times), as air is purged from the unit,
the oil level will drop.
2. With the bypass valve closed and the
engine running, slowly move the directional
control in both forward and reverse
directions (5 to 6 times). Check the oil level,
and add oil as required after stopping
engine.
3. It may be necessary to repeat Steps 1 and 2
until all the air is completely purged from the
system. When the transaxle moves forward
and reverse at normal speed purging is
complete.