518-H / 520-8 engine difference. One not smooth

[nekovt 0]

Hello,

I have a 518-H that runs well after restoring it last year. While it runs well, it shakes the whole tractor.

I also have a newer 520-8 (Maybe 1990?) and that engine is smooth as can be.

Does anyone know if there's anything I can check or something that could be wrong with the 518?

Thanks!

Brad

[TheReDStAnG 4]

Have you done a compression check, verifying that you have spark at both cylinders, fuel? Timing shouldn't be an issue as it isn't adjustable (assuming that it hasn't been opened up and marks have been changed). While running,try pulling one spark plug wire at a time. If you pull the wire and nothing changes, your problem is with that cylinder. Onan's have been known to run pretty good on one cylinder, but will cause a shake if one of the rods has let go or no compression in one cylinder. Also check that the engine is securely mounted on the tractor.