jcb JS200 Service Manual page 448
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Also See for JS200:
- Operator's manual (31 pages) ,
- Service manual (51 pages) ,
- Operator's manual (31 pages)
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Section F
3 - 6
Operation (continued)
Shuttle Function
The counterbalance valve has a shuttle function. When the plunger moves from the position in Fig. 5-1 to that of Fig. 5-2, the
parking brake release port P3 is opened to guide the pressurised oil to the brake releasing cylinder cavity. This releases the
parking brake. When the motor stops, the counterbalance valve becomes as shown in Fig. 5-1 and P3 port is blocked and the
drain port in the motor case is opened. The pressurised oil in the brake is exhausted into the motor case to activate the brake.
Fig 5-1. Shuttle Function
Relief Valve
The relief valve determines the drive force and brake force which controls the machine travel and is located on the cross line.
This valve also provides the shockless function which reduces shock during acceleration.
The relief valve is constructed as shown in Fig. 6.
a. Area differential type directly driven relief valve
b. Shockless piston
With the shockless type relief valve, reduction of shock and stress on the structure is achieved.
Relation of relief valve set pressure and adjuster amount
Per one rotation approx. 8.6 Mpa {88 kgf/cm
Do not make adjustments unless there are problems.
9803/6400
Transmission
Motor/Gearbox
}
2
Fig 6. Relief Valve Section.
Fig 5-2. Shuttle Function
Section F
3 - 6
Issue 1
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- Section E - Hydraulics
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Troubleshooting
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Questions and answers
Trouble shoot no swing
To troubleshoot a no swing issue on a JCB JS200, follow these steps:
1. Check if engine starts and operates normally:
- If the engine does not start and “Electric system abnormality” is indicated, refer to Trouble No. 10.
- If the engine starts but rotation does not change with throttle, controlling engine rotation may not be possible.
2. Check hydraulic system components:
- Inspect for sufficient hydraulic oil amount; refill if low.
- Check the hydraulic oil strainer for contamination; clean or drain as needed.
- Ensure oil levels in reduction gears are adequate; refill if needed.
3. Check for mechanical or control blockages:
- Inspect the remote control valve for:
- Low secondary pressure due to low primary pressure—apply correct primary pressure.
- Damaged spring—replace the spring.
- Excessive clearance between spools and casing—replace the remote control valve.
4. Inspect motor operation:
- If motor does not run or rotates slowly:
- Check for pressurized oil; inspect pilot piping for damage.
- Remove foreign matter between plunger and body, orifice, or dumper piston and cap.
- Repair or replace damaged parts as needed.
5. Check electrical and wiring connections:
- Inspect battery terminals and alternator wiring for looseness or corrosion; tighten or replace as needed.
These checks cover both hydraulic and electrical causes that could lead to a no swing condition.
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