Briggs Flathead Twin

[TWG1572]

Got my old Deere 116 out of storage for the winter this weekend. Changed the oil (used left over PP 5w30 - next time it's rotella 15w40 I think), put some E3 plugs in, and greased up everything that should be greased.

It felt great to be back outside and mowing again.

My wife claims I'm obsessive about lawn mowing, but I disagree.

When I was mowing I noticed it started running rough under power. I was at a loss - the carb was run dry over the winter and gas stabilized. I poked around the engine and noticed that one of the spark plug wires had fallen off. DOH! Much better.

On to my question. When looking around for the reason for the rough running, my first thought was carb. My second thought was, why bother I can't adjust it anyway? However, there is one screw on there that I could adjust - can anyone help me ID it?

It sits right below the fuel pump/carb and is pointing forward. I can turn it in and out and it sort of affects the smoothness of the engine - but nothing like if I was adjusting the main jet. It will run with the screw all the way in and out. About 3/4 - 1 1/2 turn out seems to be giving me the smoothest sound. Is it some sort of idle control screw?

It's not the screw that mechanically controls how low the idle will go, which is on the side of the carb and attached to the governor linkage.

On a different note, I'm getting a bit of a stumble when I quickly go from idle to full throttle. Any thoughts?

 

[Bluestream]

How old is this engine? The carbs will eventually need to be taken apart and cleaned no matter how well they are winterized. Is that that much work either.

 

[TWG1572]

I think my grandpa bought it in 1984, I'm not sure what he did to it. I got it in 2003 I think - it's probably due a rebuild I guess.

 

[440Magnum]

The one screw you have is probably a low-speed / idle mixture screw. Carbs like that used to have both a low and high-speed adjustment screw, but the high-speed screw was replaced by a fixed jet in most designs a long time ago.

If you're very religious about running the carb completely dry before storing for winter, it may just about never need a rebuild (especially if it has an old solid brass float needle valve instead of a rubber-tipped needle valve). What tends to ruin them is deposits from fuel evaporating out of the bowl over and over. If you run it dry, you don't get those deposits.

 

[Steve S]

What kind of sparkplugs were in there before? Before you think about rebuilding what is the compression ? Did it run good before you put it away?

 

[TWG1572]

Just to be clear, the motor is running the same now as when I parked it. I'm just being a bit anal, with the exception of the one second hesitation from idle to full throttle it runs ok. I may be crazy, but it seemed like I got a puff of air coming back through the intake when it happens. I had the air filter off and was cycling it back and fourth. Could that be happening?

As far as the plugs go, I'd always run champions to this point. They have always had some oil fouling when I pulled them, this thing will kick out a puff of smoke when starting.

Good question on the compression. I'll check tonight once I take my son to swimming. I've been wondering about that. Sounds like a good project for the night.

The bottom line is this tractor has sentimental value to me and I want to keep it running as long as possible. The small engine shop guys call me crazy every time I spend money on it, but I'm ok with that.

 

[TWG1572]

Just an update on compression - 110 PSI both cylinders. That was a cold test. I think I'm happy with that based on what I saw online.

Looks like a carb cleaning / rebuild may be in order.

 

[greenaccord02]

Those are good numbers. Clean out that carb and I think you'll be in business.

 

[Cujet]

Could be the fuel with alcohol in it. I know that my Kawasaki push mower is jetted so lean that I have to use Avgas in it to get it to run correctly. Otherwise I have to use the choke, at the "full throttle" stop. Kind of a pain.

Avgas solves that problem. I don't even burn a gallon a year in that mower, as my JD tractor does the big work.