Loosening the bolts of the cam chain tensioner can potentially disrupt the timing and tension of the cam chain, which can lead to issues like the ones you described. To bring your BMW C400X scooter/motorcycle back to its previous state, here are a few steps you can take:
Check and Adjust Cam Chain Tension: Ensure that the cam chain tension is properly adjusted. Refer to your motorcycle's service manual for specific instructions on how to adjust the cam chain tensioner. It typically involves using specific tools and following a precise procedure.
Inspect Timing: Check the timing of the cam chain to ensure it is correctly aligned with the crankshaft and other relevant components. If the timing is off, it can cause erratic idling, overheating, and engine issues. If you're unsure about how to check the timing, it's best to consult a professional mechanic.
Reassemble Correctly: Make sure that all the components, including the cam chain tensioner, are reassembled correctly. Ensure that the tensioner bolts are properly tightened according to the manufacturer's specifications. Double-check that no other components were inadvertently disturbed during the process.
Address Overheating: If the engine is overheating after the tensioner adjustment, there may be an additional issue at play. Check the cooling system for any obstructions or leaks, ensure the radiator is functioning properly, and verify that the cooling fan is operational. If the problem persists, it's advisable to have a mechanic diagnose and address the overheating issue.
Seek Professional Assistance: If you're unsure about performing these steps yourself or if the issues persist even after attempting the above steps, it's recommended to take your BMW C400X to a certified BMW service center or an experienced motorcycle mechanic. They will have the expertise and specialized tools to diagnose and rectify the problem accurately.
It's crucial to handle any adjustments or repairs related to the cam chain tensioner and engine timing with care, as improper adjustments can lead to further damage or engine failure.