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Thread: Small engine problem

  1. #1
    Senior Member
    Join Date
    Oct 2002
    In the city now.

    Small engine problem

    (I posted this over on TBN, but only got one reply. Sorry if you've already seen it.)

    This one's got me baffled.

    The engine is a Briggs & Stratton, 4 HP, made in the early 60's. It will start on full choke, first pull. If I move the throttle off choke, it wants to die. If I'm fast enough, and choke it again, it will continue to run. It won't keep running on full choke, though. Normally, I would guess some type of air leak. But here's the thing that doesn't really fit that guess: if I move the throttle off full choke, to near idle (immediately after starting it) it runs quite nicely. It seems like it could idle that way until it ran out of gas. But if I push the throttle forward, and the RPMs go up, it will quit. (Unless I choke it again.) I think the carb is a vacu-jet. I have replaced the small rubber gasket that makes up the valves and pump, and cleaned it thoroughly.

    Any ideas?

    Thanks in advance. Bret

  2. #2
    Join Date
    Feb 2004
    Was just there in God's country... Picked up, hauled tractor back here. Well, I've had simular problem with my 3hp briggs mower. and Ryobi weeder. While in TX my brother & I stopped in to pick up his weedeater and the service guy says the problem is from ethenol. (Corn is for only two things, eatin and feedin). Anyhow his illustration that most guys will run mower weeder to near empty then refill. Over time the ethenol builds up and every time you fill up it stirs up some large pockets of it causing exactly what you experianceed. Running part choked seems to help but if contaminants are bad enough it does a good job at clogging things up. said the ethenol will leave a white residue in the carb, and dry rot the tubing gas lines. THE SOLUTION was to use an additive that causes the ethenol (and water) to emulsify thereby allowing better combustion. For his shop he checks the gas by pouring into quart jar with 1/2 cup water, shakes it up and lets sit for 15-20 min. Then what you'll see is the separation of fluids: beaded on top will be little balls of nitrogen, gas, then a ethenol layer then the water. They siphon off the gas and throw out the rest. While in TX my GMC set a SES error code 0430, major engine probs. Guy at Autozone here at home said it was bad gas, (probably picked up in AR) and to use Sea Foam additive in fuel, and remove both battery cables for about 10 minutes. Had about 25 gallons in tank used one can of stuff and light has been off ever since. I've also switched to local COOP gas with no ethenol. That stuff causes more problems and less gas mileage and the subsudies cause us all more out of pocket taxes. We need to stop proppin up the oil companies to make the stuff and cut off the farmers that grow and sell good corn for bad fuel. Sorry but the Gov't is on the wrong path for America!!! Hey JazzDad, is that a sax strap you got on? hope this helps.

  3. #3
    Senior Member
    Join Date
    Jun 2009
    Lawn Mower Forum - Lawn Mowers, Lawn Tractors & Lawn Care Forum
    It's the carb
    Post it here and you'll get some answers

  4. #4
    Junior Member
    Join Date
    Dec 2009
    The problem is the fuel air mixture. This is not a new thread,I see, you may have fixed it. You may be able to correct it with an adjustment, the bowl may have water in it or cleaning the carb. Not enought fuel not enough air at full choke.

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