# B&S 3.5 HP Classic Throttle Free Engine Surge



## Cankuwicasa (Sep 11, 2012)

Recently acquired a 20" Murray with the above-mentioned engine. After doing some research, I cleaned the air filter, cleaned the carburetor, replaced the govenor spring, replaced the diaphragm, replaced the primer bulb (I still don't think it's working, but it was dark and I couldn't really see what I was doing), & changed the oil. Parts shop had no govenor idle springs in stock so I couldn't replace the one that was missing from the mower. Have not yet replaced spark plug, but intend to do so tomorrow. Will also remove shroud and examine wind vane mechanism. Blade was in atrocious shape. Will sharpen it tomorrow. Mower started but surged badly. Will mow, but not very well. A vertical tab on the the throttle control mechanism had been bent out of vertical. I bent it back. The entire throttle mechanism seems to move a bit tightly. However, I don't really know how smoothly or freely it should move. Appreciate any comments that might addresss the issue of the engine surge.


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## usmcgrunt (Sep 16, 2007)

Hello and Welcome to Hobby Talk.The tab you bent is for setting the maximum governed engine speed.By bending it back,you may have reduced the engine RPM's quite a bit.A missing spring could also be part of your surging problem.If you have a tachometer,I would set the RPM's in the 3000 to 3200 range.Here is a link to the service manual,if you need it.Hope this helps.

http://dl.dropbox.com/u/12502267/B&S Service Manuals/01_270962SingleCylinderLHead.pdf


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## Cankuwicasa (Sep 11, 2012)

Thanks for the reply and the link, looks like it might be helpful. Will get new plug tomorrow and try to find a govenor idle spring. Also intend to examine key way to insure there isn't a partially sheared key involved. Will go from there and see how everything works.
:wave:


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## Cankuwicasa (Sep 11, 2012)

Okay, took carb back off the mower and examined. Think I boogered up the diaphragm when I put it in. Wrinkled and distorted.  Removed entire carb from a yard sale clunker I had laying around and put it on the mower. Runs like a champ.:tongue: Also added a throttle control. Tomorrow will attempt to install set of adjustable wheels salvaged from the clunker.


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## usmcgrunt (Sep 16, 2007)

Glad to hear you were able to bring Frankenstein back to life.It sure is nice to have spares laying around.Good job.:thumbsup:


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