B&S 20hp surging,

I have the Murray in the thread" Murray engine troubles" (on the Tractor forum Murray engine troubles - TractorByNet.com) and have it running..again and for now. It seems it is constantly" hunting" as i mow. This happened once before and i trouble shot it to the fuel pump but now i am not sure. This engine is on its very last leg so i am not investing much. $$ into it any more.

It seems every time i turn it off now it pops about 1 second after the engine stops. Kinda weird.

Can a backfire cause problems with these vacuum fuel pumps?

How can i troubleshoot the governor? If it is the governor can i bypass it? Like i said this motor is on its last leg and if i can get one or two more mows out of it i am happy.

The engine is a B&S 20hp opposed flat head twin. Any help will be appreciated.

The afterfire normally won't hurt the engine or any components. it could be a governor problem but is most likely a carb related issue. thirty years ago most of the mowers afterfired and nobody complained now if one afterfires it a major ordeal and sometimes can't be eleviated.

The afterfire, wasn't my main concern, it has before, backfired during running, and that had me wondering about the damage it might cause.

Is there a way to bypass the governor to tell if it's the problem?

If you hold the throttle steady and it is the carb it will continue to run poorly. if the running is steady then it is probably the governor. most likely it is a fuel/carb problem and not the governor. governors don't fail very often. usually when a governor fails the engine goes wide open .

ILENGINE said:

If you hold the throttle steady and it is the carb it will continue to run poorly. if the running is steady then it is probably the governor. most likely it is a fuel/carb problem and not the governor. governors don't fail very often. usually when a governor fails the engine goes wide open .

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I assume you mean hold the throttle, at the carb, and not by the throttle lever on the dash? It has a throttle lever, connected by a cable to the carburetor. This is not the type of engine that has a self regulating throttle, like newer units.

yes hold the throttle at the carb

Ok will try that today. Will update.

Well, it ran real bad, almost died when I held it. So I pulled the carb off, and went through it with a kit I had left over from before. I had purchased a complete rebuild kit including a fuel pump and only installed the pump before. So I cleaned out the carb, and installed new float valve. Couldn't get old seat out, it's a press in affair, but is nothing more than a brass cylinder with a small hole in one end. I blew it clear and installed the new valve (pin or what ever it's called). New gaskets and re-installed it. It started surging again, but as I took it out and mowed about 2hrs with it the surging seemed to diminish a bit. Oh well, as long as it mows a few more times i am happy. I have never expected this thing to run very long, with the valve repairs i have had to do, so I am glad for every mowing I can squeeze out of it.

Last year, it cost me $150 to have someone come in and mow, so I figure that's $150 I put in the bank every mowing i can get. That much more saved and towards the new mower. So far, 5 mowings this year. Pretty soon, this area will dry out and won't need mowing till next year, but since it just rained again, all weekend, I'm sure there's one more mowing gonna be due before the dry season sets in.

I moved your thread to the Small Engine & Mower Repair Forum. :smile:

Does it idle okay? Have you adjusted the high speed jet? What about the float level? You may only need to adjust the screw on the bottom of the float bowl to smooth things out.