Gas Leak - Old Gas Question

Doing some work on a Bolens by MTD with a Briggs and Stratton 500e 140cc mower that some guy in the neighborhood gave me. Wouldn't run, carburetor was dirty and the jets were clogged. Disassembled and completed a full clean out on the carb/gas tank. Cranks on 1st pull and runs just fine now. Problem is that after I run it and let it sit, it leaks fuel through the carb into the foam air filter and down on to the deck through the plastic housing. It's not new fuel, it's old, yellow and varnished, similar to the fuel that was stuck in the carb when I cleaned it.

Frustrated, I removed the carb again and picked up the mower to the tailgate of my truck. There is it, that old, yellow, varnished fuel coming out of the engine block where the carb attached. I tilted the mower on its side and drained all that I could possible drain without tipping the mower over. There in lies my question... can old, yellow, varnished fuel remain in the engine and not combust, yet let fresher gas keep the engine running? I'm hoping by draining all the old gas out by tipping it on its side will solve the issue.

Thanks in advance for any insight!

Drain the crankcase and get all of that goop out.

Then fill with oil, run 15 minutes and change oil again. You may want to do this a second time.

As long as the needle and seat are in perfect working order, this shouldn't happen again. But it's a common occurrence on gravity-fed systems because needles and seats are usually NOT in perfect working order.

The easiest fix is to install a fuel shutoff valve and keep it closed when the engine isn't in use.

AK is that the E series with the Carb on the Left/Port side of the engine ???? The port side is the left side of the engine when you are behind the mower looking to the left......

That is the newer style engines with the all plastic carbs and they do not like old gas and ethanol gas... The big white piece in there is the jet and needs to be popped out and cleaned well....

It needs to be gently taken out and oiled before putting back in.......

You'll be in good shape after doing that and the tank usually just lifts up and it's a matter of a good cleaning ~!~!

Let us Know Mon Ami ~!~!

cpurvis, that is the next step tonight. Went ahead and also picked up a pack of fuel shut off valves since they were cheap and will be here quick via Amazon Prime. Put the carb back together and did the old blow test, air passes through when down and air stopped when float is up, so the needle should be seated properly. Between the shut off valve and a few oil changes, should be in business.

Boudreaux, yes Sir, it’s the E series with the carb on the port side. Many YouTube videos showed cleaning this carb without removing this piece, which I guess for them, they were lucky as I don’t see how anyone could properly clean this carb without removing that piece.

Thanks for the insight guys, much appreciated! Will let y’all know the results in a day or so.

Seems to have done the trick, after the drain and new oil, ran for about 20 minutes and sat overnight. No drainage. Still will put in a shut off valve once they arrive before I sell it though, I just like that idea.

Thanks again y'all!

AKavanaughSC said:

Seems to have done the trick, after the drain and new oil, ran for about 20 minutes and sat overnight. No drainage. Still will put in a shut off valve once they arrive before I sell it though, I just like that idea.

Thanks again y'all!

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Good to hear.

A lot of stuff you see on You Tube is some what akin to what you flush down the toilet.
All you need to post, is a video camera ( even a phone will do ) and a computer.
Some labs have trained monkeys to make U-tube post which is a wast of time as baboons have been able to do it for years.

Also be careful using cheap taps bought on line.
They all come from China.
Some are good and some are bad.
I had a batch from Jackmax ( a local aftermarket parts wholesaler who I no longer deal with ) that had neoprene seals which swell then go to sticky goo when exposed to fuel for extended periods.
Cost me a fortune in warranty repairs.