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Hard cranking 448 Case
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18 Hp Onan

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Marty

10-24-1999 10:30:43




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I am able to turn the engine without the spark plugs in as one should; however, when I go to start the engine it turns hard and when it is about to fire it stalls. I have read on the web about others with Kohler engines that have problems with the compression release system. I can not find anything about this in the repair manual. Would anyone have any idea where the flyweight spring is or a small tab that opens the exhaust valve that releases the compression that allows the engine to turn freely to start?

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Mark

10-27-1999 16:36:36




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 Re: Hard cranking 448 Case - 18 Hp Onan in reply to Marty, 10-24-1999 10:30:43  
Marty if it ran alright before this happened check all the battery connections--ground at the engine-both sides of the relay near the battery and at the starter.take them apart and clean them with a wire brush. In my expirence with these engines seldom the starter is to blame unless it has many thousand of hours.e-mail me if you need more help



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John

10-27-1999 07:55:15




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 Re: Hard cranking 448 Case - 18 Hp Onan in reply to Marty, 10-24-1999 10:30:43  
It has been a long time since I worked on small engines and I am not familiar with Onan, but it might be an ignition timing issue. On some engines if the flywheel key shears and throws the timing too far in advance, it will want to fire too far before TDC, forcing the piston down in the opposite direction.

I am not saying it is a flywheel key (this is usually a problem when the blade is attached directly to the shaft and you hit a stump or rock,causing the key to shear between the flywheel & crank), but check the timing.

Are the spark plug wires on the correct cylinders?

If the engine has been disassembled, valve timing may be off by a tooth or two at the cam.

If you hadn't taken the plugs out and turned it over, I might have suspected hydraulic lock from excessive fuel or oil in the cylinders.

Just guessing, but I hope it gives you some options to explore.

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Mark

10-25-1999 17:31:08




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 Re: Hard cranking 448 Case - 18 Hp Onan in reply to Marty, 10-24-1999 10:30:43  
If this is an onan,Idont believe it has a release



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Marty

10-26-1999 17:08:22




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 Re: Re: Hard cranking 448 Case - 18 Hp Onan in reply to Mark, 10-25-1999 17:31:08  
Mark, Would you have any idea what would cause the engine, that I can turn by hand with the spark plugs out, to turn hard and stall upon firing? Is there any way to test the starter? I have tried a larger new battery!



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Marty

10-26-1999 17:08:11




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 Re: Re: Hard cranking 448 Case - 18 Hp Onan in reply to Mark, 10-25-1999 17:31:08  
Mark, Would you have any idea what would cause the engine, that I can turn by hand with the spark plugs out, to turn hard and stall upon firing? Is there any way to test the starter? I have tried a larger new battery!



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