Turbodriven
Active Member
- Joined
- Aug 18, 2023
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The mower is a Gravely 260z with (let's just call it) a brand new engine/fuel system and for the sake of argument, a new deck/blades/pto. Engaging blades causes a momentary drop of a 4-500rpms but then quickly high idles again at 3400+. About 10-20 feet into mowing however (sticks forward) the hydro system binds and causes the motor to lose significant rpms (tiny tach hooked up to watch rpms). From an operating speed of 3400+ down to 1700 or even less depending on load. Going up a hill for example causes rpms to go so low it almost kills the motor. Pulling the sticks back to neutral at any point causes the rpms go back up to 3400+ (within a few seconds).
1. When on jack stands, operating the left stick full forward has no effect on rpms. Wheel spins like it should and literally the rpms don't even dip 1 rpm. Same with the right stick.
2. When mowing, operating the left stick (only) full forward from a stop causes rpms to drop to well under 2000. Same with right stick (only). No difference between the left and right. Both independently cause the rpms to drop significantly.
3. With belts off, both pumps feel smooth (hand spinning the pulleys). Maybe that says nothing but it's worth noting.
What could be wrong in the system pictured to cause this? Blockage on the pressure side? But on both sides? Seems highly unlikely that two independent systems would have pressure side blockages? The filter is on the suction side and shouldn't cause something like this right? And even if it was dirty/blocked it has a bypass to let fluid go through unfiltered.
Note, the system is filled correctly with 'what feels like' clean fluid which is the same consistency as the new bottle of manuf. recommended fluid I have. Nothing abnormal. It also has a brand new drive belt.
1. When on jack stands, operating the left stick full forward has no effect on rpms. Wheel spins like it should and literally the rpms don't even dip 1 rpm. Same with the right stick.
2. When mowing, operating the left stick (only) full forward from a stop causes rpms to drop to well under 2000. Same with right stick (only). No difference between the left and right. Both independently cause the rpms to drop significantly.
3. With belts off, both pumps feel smooth (hand spinning the pulleys). Maybe that says nothing but it's worth noting.
What could be wrong in the system pictured to cause this? Blockage on the pressure side? But on both sides? Seems highly unlikely that two independent systems would have pressure side blockages? The filter is on the suction side and shouldn't cause something like this right? And even if it was dirty/blocked it has a bypass to let fluid go through unfiltered.
Note, the system is filled correctly with 'what feels like' clean fluid which is the same consistency as the new bottle of manuf. recommended fluid I have. Nothing abnormal. It also has a brand new drive belt.
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