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Discussion Starter · #1 ·
Hey everyone, just looking for some help with my Case with the 18 hp Onan. It is throwing alot of blueish smoke out the exhaust, and burning quite alot of oil. My thoughts are Pistons and rings? Maybe valves? Any help would be greatly appreciated!
Thanks
 

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My suggestion would be to do the following.

- remove the heads and carry out a decarbonizing as per the service manual Pay attention to the undersides of the valves.

- set the valve lash so that you know that the valve train is opening and closing correctly.

- with the heads back on and torqued down, do a compression test

- then do a leak-down test.

That's the way to assess what's going on inside the engine.
 

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Discussion Starter · #3 ·
Thank you for the help. Now I know where to start. I am new to this website so is there instructions on how to do all that on here? I am" mechanically able" ( i guess thats the best way to say it) i just have never done those things with this motor.
Thanks
 

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Onan Master, new and used parts.
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case446
you have a rare BG engine
3.25 bore 3.00 stroke (49.8 ci.)
rated at 18.0 h.p..

pistons and rings, still ava. (in pairs) rods and crank ???

you could install the B 48 rods and crank.
good luck. boomer( the used onan parts guy)
 

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Boomer is the best but................. why get ahead of yourself?

Now is the time to do those things I mentioned so that you can DIAGNOSE what is truly wrong with the engine you have.

If you don't understand what a leakdown test is... perhaps this will help.

http://www.motorcycleproject.com/motorc ... kdown.html

We have manuals on Onan and Kohler engines in the Library that explain how to decarbonize the engines.

What else would you like to know?
 

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Look at the gaskets you remove to check them for damage. If they look pretty good, then go buy a rattle can of aluminum spray paint and just before you are ready to install the heads, spray paint both sides of the gaskets. Leave them hanging up until they get tacky and then install them. Torque the head bolts down in the proper sequence outlined in the Service Manual. Those will get you by for the moment. Start your engine, let it warm up and then re-torque the head bolts. Then you can take your compression readings and conduct the leakdown test.
 
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