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Some of the common problems that plague Onan engines.

Carbon build up on heads and pistons in generators- Generators often will carbon up much more than an engine used on a tractor. If your engine is knocking, take the time to perform a compression test before assuming the worst. Good compression or high compression could indicate carbon buildup that has gotten bad enough to creat a knock. Confirm by pulling the heads.

Intake or exhaust seat coming out- The intake and exhaust seats are hardened steel pressed into the aluminum cylinder block. If your engine ever runs hot you run the risk of the aluminum expanding and the steel seats becoming loose. The only tip is to maintain your engine. Keep it clear of grass and debris. Check and change your oil regularly.

Flywheel magnets- Flywheel magnets will often come loose from striking or dropping the engine. They may also loosen from rust getting under the glue that holds the magnets on. You may only re glue the magnets if they are not cracked or destroyed. Only use a high quality black super glue for steel. Magnets are not available. If your magnets are junk, the flywheel will need to be replaced.

Intake manifold leaks and intake manifold gaskets- On many of the two cylinder engines, Onan uses a two piece intake manifold. This manifold is assembled and sealed at the factory. If your engine is running erraticly, check the manifold. A visual check can work, or take the manifold off and spray carburetor cleaner at the seam. Any leaks will show through. If it leaks, replace it. A silicone repair will only last about a week.