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Eratic engine speed

JoeC's Avatar
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05-25-04, 08:39 AM   #1  
Eratic engine speed

I am trying to help out a friend with her mower, a lawnboy 8243AE push mower, 2 cycle engine with walbro carb, here is the problem: The govenor spring was broken on it so I replaced that, unfortunately the engine speed is still eratic, I adjusted the spring tension and the best it will do is to hunt around at high speed, but it falls back to a low idle if the mower is tilted even slightly, or hits a medium sized bump, then has to be throttled down to an idle then back up to return to operating speed. The govenor seems to be controled by both the spring and engine ?vacuum? (that is air bieng blown out from the rotating assembly) via an airfoil type device. The engine will rev up and run properly if I manually hold the govenor. I am not sure what to check, please help me out.

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puey61's Avatar

Join Date: Apr 2004
Posts: 3,224

05-25-04, 03:56 PM   #2  
Oh Boy!

You supplied a model number but not a serial number. There are three model years for this model - '86, '87 & '88. I looked at the 1987 and it shows this engine has an air-vane governor, whereas the momentum of the flywheel dictates the need to be governed. The governor vane is attached directly to the throttle shutter, using the coil spring you mentioned adjusting the engines' RPM at a factory set rate. It sounds as though you have this correct. I am thinking you have a carburetor in need of a thorough cleaning. Generally, removal and disassembly of such and merely flushing everything with a quality spray cleaner (I recommend Briggs Cleaner, part number 100042) is all that should be required. Most times, replacement of parts can be avoided with these carbs. Try this and let us know what happens.
One item of note: It is important for the vane to be clean of any residue, so that it is not additionally weighted.

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