Mower Runs Sluggish...But Then RunsFine?


Old 08-25-17, 05:57 AM
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Mower Runs Sluggish...But Then RunsFine?

I own a Toro 21" 4 cycle mower that recently has begun to run sluggish on a full tank of gas. However, when it is close to running out of fuel it begins to run both fast and smooth. Spark plug has been changed but checked nothing else yet.

I would welcome insights & suggestions.

Thank You!

Tim Clark
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Old 08-25-17, 07:13 AM
Join Date: Dec 1999
Location: Cleveland, OH USA
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It is possible that the gas tank is not venting properly and you are creating a vacuum in the tank when it is full. When the tank is almost empty, there is alot more air in the tank so it runs better. Try loosening the cap on the tank when it is running poorly and see if it improves. If it does then replace the gas cap.

- Peter
Old 08-25-17, 09:27 AM
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It could be that the carburetor is worn or out of adjustment. The mower may be running rich when the tank is full but as it nears empty the mixture leans out. But without knowing exactly what engine you have we it's hard to offer specific recommendations.
Old 08-25-17, 11:08 PM
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Have you checked the air filter yet?

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