When you replaced the crankshaft bolt and belts on your 2001 Montero Sport Ltd, and it now turns over but does not start properly, there could be a few potential issues to consider:

1. **Timing Belt Misaligned**: With the replacement of the crankshaft bolt and belts, it is important to ensure that the timing belt is properly aligned. If the timing belt is misaligned, it can lead to issues with engine timing, causing the jerking and failure to start correctly.

2. **Faulty Crankshaft Position Sensor**: The crankshaft position sensor is responsible for monitoring the position and speed of the crankshaft. If this sensor is faulty or not aligned correctly during reassembly, it can lead to starting issues.

3. **Improper Belt Tension**: When replacing belts, it is crucial to ensure that they are tensioned correctly. If the belts are too loose or too tight, it can cause issues with engine operation, leading to the symptoms you are experiencing.

4. **Fuel Delivery Issues**: Check the fuel system components, such as the fuel pump and fuel injectors, to ensure proper fuel delivery to the engine. If there are issues with fuel delivery, the engine may not start or run correctly.

5. **Ignition System Problems**: Check the ignition system components, such as the spark plugs, ignition coils, and spark plug wires, to ensure they are in good condition and properly connected. Faulty ignition components can prevent the engine from starting smoothly.

It is essential to double-check all the work you performed during the replacement of the crankshaft bolt and belts to ensure everything is correctly installed and aligned. If you are unsure about any steps you took during the repair process, it may be necessary to retrace your work and make sure everything is in order.