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Old 14-06-2009, 12:10 PM
ferrarif360cs ferrarif360cs is offline
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First recorded activity by GardenBanter: Jun 2009
Posts: 3
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Quote:
Originally Posted by stoneattic View Post
I have a cheap MTD mower with a 5hp B&S engine. The "automatic"
throttle lost a spring and the plastic piece that appears to control the
engine speed (the vertical piece in this pic:
http://www.kichline.com/chuck/fixit/...s4hpspring.jpg)
is broken so I converted it to a manual throttle cable. I connected the
cable to the piece that is connected to the plastic piece in the above
pic via a rod with a loop in it. (Hopefully the pic and description
make sense).
The thing is that if I'm sitting still the cable controls the RPMs as
expected but as I move the mower around RPMs fluctuate even if I'm not
cutting anything. I except the RPMs to drop when there's a load from
cutting but it seems random and will surge and drop.

Any thoughts? Is there something else that controls engine speed that I
haven't found on this engine?

thanks in advance!
If I remember rightly there is a small air vane that sits in the air stream from the cooling fins on the flywheel. This keeps the engine at a reasonable constant speed setting, I suppose it is feasible this vane is damaged or something. The "throttle" control you mention is connected to that spring via the linkage. It tensions the spring and causes the air vane to be less effective in slowing the engine down.
I hope I explained this ok.