Onan Microlite 2.8 KV-B teardown

Onan is a popular manufacturer of gensets – generator and motor sets – for the RV industry. The 2.8 kilowatt Microlite in a 1991 Airstream B-Van suffered as many of them do. It had only run a bit over 100 hours in 16 years and had been otherwise neglected. Varnish from drying gasoline had built up in the carburetor, linkages had broken or become stiff, and things had become a bit dirty. It was hard to start and didn’t quite run right when it did run. So the time had come to clean, adjust, repair, and fix it up. This kind of thing is a ‘do it yourself’ thing because the time requirements in a shop tend to create a bill that is close to the cost of a new genset.

To do it yourself, you will need some expertise, a few common tools, an Onan service manual for the genset, and a few of the appropriate personal attributes that lead towards a successful outcome such as patience, intelligence, good study habits, mechanical aptitude, experience, knowledgeable friends, resources, and more.

This is part one of the story of one such back yard effort. It is not a how-to but rather a caution for you to see what is involved and what someone else did. You should not attempt this sort of project unless you understand the risks involved, both financially as well as in terms of safety, and have competence in good decision making. This is the first of entries planned to describe how this effort proceeds. There will an attempt to explain what the various components do and how they work. The hope is to help you better understand some of the systems that make your RV experience more enjoyable.

The first job is to get the genset out of its nest. That is a matter of removing two screws on flanges holding the genset down, removing the exhaust pipe from underneath, and then disconnecting the battery and ground terminals. Inside the B-Van, the power feeds from the genset to the transfer switch needed to be disconnected so the wires could be pulled. Then the genset could be pulled out a bit and the fuel line and power cables could be disconnected. Once everything is free, the genset could be removed from its nest. The genset is heavy and awkward so take due precautions to protect yourself and your equipment when moving it.

(click on thumbnails to see larger picture)

Nude Onan After the cover and the shrouds to control airflow and the carburetor have been removed, this is what you get. The fan is on the left and the muffler is on the right. At the top is the starter. You can see a plastic bag stuffed into the hole where the carburetor attaches to the cylinder. That is an attempt to prevent unwanted crud from getting into the cylinder.

carburetor in cleaning The carburetor was removed so it could soak in a cleaning solution. All rubber O-rings and other non metal parts had to be removed else the cleaning solution would dissolve them. Gasoline varnish is tenacious and difficult to remove. The carburetor has many small holes that get clogged and the varnish must be cleaned out of the for the engine to run properly.

onan shrouds in cover Here are the shrouds and some other parts stashed in the genset cover. They will need to be cleaned. Detergent and water will usually do for these.

onan small parts collectionOne of the big challenges is keeping track of the miscellaneous small parts such as fasteners, springs, and other esoterica. A partitioned tray like this one will handle a small job like the genset.

Note that you will need to secure the stranded things in the empty nest. If you don’t stopper the fuel line, you will leave a trail of gasoline behind if you try to head down the road (don’t ask how I know!). The battery positive line needs to be protected so you don’t get any shorts. Any loose pieces should be tied down until you get the genset back into its nest and re-attached.

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