Adjusting Valves on Onan Engines: A Comprehensive Guide

Onan engines, commonly found in generators and other small industrial equipment, require regular maintenance to ensure optimal performance. One crucial aspect of this maintenance involves adjusting the valves to maintain proper clearance. This guide will walk you through the process, from preparing the engine to making the necessary adjustments.

Tools Needed

Feeler gauge to measure valve clearance Socket set and wrench Screwdriver if needed for adjustments Service manual for the specific model

Steps to Adjust Valves on an Onan Engine

Prepare the Engine

Before beginning the valve adjustment process, it is essential to ensure the engine is in a suitable state for maintenance. First, allow the engine to cool down to prevent any expansion issues that could interfere with the precision of the adjustment. Next, disconnect the battery and spark plugs to prevent any accidental starting during the maintenance process.

Access the Valves

To access the valves, you will need to remove the valve covers using a socket wrench. This step exposes the rocker arms and the valve stems, making them accessible for adjustment.

Set the Engine to Top Dead Center (TDC)

To set the engine to Top Dead Center (TDC), rotate the engine manually by turning the crankshaft until the piston is at TDC during the compression stroke. You can confirm TDC by aligning timing marks on the flywheel or checking the position of the intake and exhaust valves, which should both be closed.

Check Valve Clearance

Use a feeler gauge to measure the clearance between the rocker arm and the valve stem. Consult your specific Onan engine service manual for the exact clearance specification, typically given in thousandths of an inch. Common clearances for Onan engines are around 0.005-0.010 inches, but it is crucial to refer to the specific model's guidelines.

Adjust the Valves

If the clearance is not within the specified range, you will need to adjust it. Begin by loosening the lock nut on the rocker arm. Then, use the rocker arm screw to make the necessary adjustments until the feeler gauge fits snugly between the rocker arm and valve stem, ensuring a fit without forcing it.

It is important to note that not all small engines have adjustable valves. If you encounter issues with the valves, it may be necessary to perform a valve job or a rebuild.

Post-Adjustment Procedures

AFTER the valves have been adjusted, ensure that all the covers, bolts, and nuts are securely fastened and that the engine is fully reassembled. Finally, perform a test run to check the engine's performance and ensure that the valve adjustments were successful.

Conclusion

Maintaining and adjusting the valves on an Onan engine is a crucial part of its routine maintenance. By following the detailed steps outlined in this guide, you can ensure that your Onan engine operates at peak performance. Remember to always consult the specific service manual for your model and take the time to perform the necessary tasks accurately.