One thing I noticed right away was a lot of oil under the generator.
I struggled with my Onan 4BGE for the better part of a year before I simply bit the bullet and replaced the entire ignition system. Turns out, when you identify aftermarket, non-Onan parts for the starter motor, and the ignition coil, you can replace every electronic bit on the generator except the voltage regulator and the control module for less than $200. You can replace those last two components for $300.
So you can replace every electronic part of the generator - everything but the mechanical motor and the generator head - for $500.
The number one killer of generators is lack of use. Monthly exercise under load is
required. There are 2 main reasons:
1) The carburetor will gum up if gas sits in it. Replacement carbs are around $300. They can be tricky to rebuild without having leak problems afterwards. Some generations of Onan they list the carb as unserviceable for that reason. It is important to have fresh gas, heat, and vibrations agitating the internals of the carb once a month.
2) The copper slip rings tarnish with lack of use. This causes an increase in resistance between the brushes and the slip rings. High brush resistance can smoke the voltage regulator. Flight Systems sells a "slip stick" that you can use to polish the slip rings.
But - if your generator has an oil leak, you may have a serious mechanical problem with the
engine. The engines on these things are generally bullet proof.
