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Blade REQUIRED for engine to run?


guy48065's Avatar
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09-08-14, 06:59 AM   #1  
Blade REQUIRED for engine to run?

At a flea market yesterday I saw one dealer start up a bare 5HP horizontal motor on the ground and it ran perfectly. I took home a vertical shaft lawnmower that had a bent blade. I started the mower without the blade and it did run--but the governor allowed the speed to fluctuate 2X per second (wow-wow-wow-wow-).

It ran fine with a new blade installed.

What's the difference? Can a governed gas engine be made to run smoothly without a blade (flywheel)?

 
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Pilot Dane's Avatar
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09-08-14, 07:35 AM   #2  
Yes, an engine can be made to idle and run smoothly without a blade. In fact that is how they should run. Your carburetor might need adjusting or cleaning if it's surging.

 
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09-08-14, 09:35 AM   #3  
That's what I was hoping to hear.
Now I just need to find the mixture adjustment--if there is one. This is a fixed-speed mower (21-inch Craftsman with 6.5HP B&S) and a quick look didn't find an adjustment. Looked at a handful of Youtube vids of this same engine/mower and none showed how to adjust the mixture. There is a tab to move to tension the governor spring to set the running speed--but is that all there is? Is this an EPA non-adjustable carb?

 
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09-08-14, 10:17 AM   #4  
Generally engines that are to be run without a blade have a cast iron flywheel instead of aluminum to provide the necessary centrifugal force to keep it running smoothly. Without it, it will probably kick back violently eventually and it may not hold up to it.


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09-08-14, 10:32 AM   #5  
I agree. In small engines class in school, lawnmower engines (light aluminum flywheel) would always run better/ more balanced with the blade on.

 
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09-09-14, 07:54 PM   #6  
I didn't know non - adjustable carbs were being used on lowly push mowers.

 
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