older onan generator

atlarge54 · Sep 4, 2012

Just brought home an older 2500W onan generator and am trying to get spark. The model is 205AJ. With the plug clamped to a clean grounded spot I cant see any spark, however I can feel voltage when I touch the plug and pull the rope. I did try a couple different plugs. My next step will be to pull the flywheel and look at the points. I've never had a onan before, anything that I should know about setting timing, etc. while I've got the flywheel off?

Thanks

old · Sep 4, 2012

Is it the engine that sort of looks like a VW engine cut down to 2 cylinders?? If so at least all the ones I have messed with have the points mounted external of the flywheel so they are easy to clean etc. The one I have has a little box sort of thing on the engine with to screw holding it on and the points sit under that box.

atlarge54 · Sep 4, 2012

No, it looks kind of like a K-series Kohler.

old · Sep 4, 2012

Don't know that engine then. The only Onan engine I have messed with are the 2 cylinder opposed air cool type which where like the VW bug engine cut in half

joe csuti · Sep 5, 2012

If you can't get any info here as to point setting,timing etc,goto ebay & type onan 205aj in search,two operators/parts manuals listed,although a little expensive.Most of the eng used on onan generators were built by studebaker.

atlarge54 · Sep 5, 2012

Got lucky on this one, cleaned up the points and carb now it lives. It did have a condenser throw a few sparks out the rear end, got her all buttoned down and seems to be ok now.

The guy at the local mower shop warned me that Onan parts are VERY expensive. These points are pretty wierd they have a little coil spring and don't pivot but mount on a little fiber block that slides.

Now I have to fix the recoil or be forced to wind the rope "old school".

El Toro · Sep 6, 2012

We used Onan generators at work for powering our instrumentation and AC in our heavy field dynamometers. We switched to diesel Onan's when the Army decided to have all engines diesel.
We received very good service from the Onan generators. The larger generators only turned 1800rpm's that were quieter when running. At one time we had a Lister diesel generator and it made more noise than the two engines powering the dynamometer. It wouldn't shutoff and started using the engine oil. We were able to stop it by blocking off the air intake. We replaced it with an Onan. Hal

Billy Shafer · Sep 6, 2012

If you will post the full model and serial number. I can tell you when it was built and get you the information you need.

Onan parts prices for the older Onan units are very very expensive. I think they are doing it. To force people to buy new units. I priced a start solenoid today. 193.25 I found an after market one for 11.00.

StudeBaker never built Onan engines. They did own Onan for awhile. But Onan built most of the older engines.

Onan tech since 1980.

atlarge54 · Sep 7, 2012

Thank you Billy Shafer! When I saw this had an Onan engine I just about didn't even look at it, but the gambler in be said to roll the dice. I've since learned that parts and information on these motors isn't easily found.

The model is 205AJ 1M/1A, ser. no. 56B539263

The one thing I might be interested in is an exploded view of the recoil. The generator came with the recoil in a box and it appears the fastener that holds the recoil together is worn off. For my needs I'm ok just using a rope to start, but it would be nice to have it properly assembled. This thing really starts easy and runs great.

Billy Shafer · Sep 7, 2012

Built in May 1956. Email me and I can send you the sheets on timing and repairs.

atlarge54 · Sep 7, 2012

When the PM feature starts working I'll send you my email address.

Thanks

older onan generator

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