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Briggs&Stratton cab "gummed"(?)

Helping a friend. Generator with B&S engine sat for about 3 years with gasoline in the tank. We got it started, but it ran only briefly (w/ lots of manual overide on the throttle contol lever), then it died. From trying to re-start, wound up with fuel leaking out of carb. Stopped working on it for a few days.

Somebody then took out the fuel.

Later, I took apart the carb (and wound up with a handful of parts and no diagram). Sure enough, lots of yellow gunk in the bowl and around some of the parts. I cleaned out the gunk, reassembled it (no parts left over). Put in new fuel and some Stabil. (And replaced the slightly fouled spark plug.) Still won’t start.

I’m thinking that one of the fuel tubes or the jet is still gunked up. Is there any solvent I can soak them in to try to clean them?

(Man at the service/parts store said usually have to replace the carb, but for $100, I’m willing to try a little harder to clean it out.)

I usually just use aerosol carb cleaner when cleaning small engine carbs.

Yup, Fordman nailed it. You will need to spray the carb cleaner thru the jets, not just the venturi tube of the carburetor. Therefor you will have to disassemble it again. Is the needle and seat good? The needle might be rubber tipped, and deteriorated. Replacing the carb is totally unnecessary.

I think that spray carb cleaner is mostly, if not entirely, lacquer thinner. I have used LT for the same purpose, and it’s much cheaper. It just has no sprayer.

I agree with the carb spray, but you should be able to get a rebuild kit for about $20 and that would be worth getting. Remove the idle mixture screw and spray in that orifice too. first tighten it gently until it stops, counting the number of turns. Remove, spray, reinstall and gently bottom it out, then back off the recorded number of turns.

If one of the jets or passages is clogged up, you may have to open it up with a thin wire or needle.

Thanks for the excellent advice. I am already trying to get a carb rebuild kit. I had figured I might need thin wire to clean out some passages. I had forgotten about commonly available carb cleaner, which I have used before for other things.

I hope to post back with results, but this is not a rush job.

Also check the float. Not sure if the rebuild kit come with one but those things are hollow. It it has a hole or crack in it somewhere, it will fill up with fuel will and will be too heavy so the needle valve will not shut the fuel off causing the bowl to overfill.

Yes, my local expert and I suspected a defective needle valve and/or float. The float in this one is plastic. I did not see any gasoline inside it, nor could I see any leaks. The B&S parts breakdown picture does not even show the float! When I have it apart again I’ll try to find a way to test for leaks.

(I have vague memory of people boiling the old metal floats to drive out the gas, and then soldering up the leak hole. Am I dreaming, or am I confusing that with toilets? I did “rebuild” a carb one time. Around 1973 there was a carb problem in the '67 Mustang that Mom had handed down to my brother. I got the kit – needle vlave, float, and whatever – and installed it. Beats me how I knew what was wrong or how to repair it.)

I had the same problem with my generator. Just replace the parts with the kit. I had to soak mine for a couple days in Seafoam and still replaced the jets. There are very very small holes that get clogged. You don’t always get the main jet in a carb kit either so go on line to Briggs or Jacks Small Engine and look at the parts list and what comes with the kit. It’ll show all the main parts for the carb. I really doubt it is the needle valve unless it was sticking badly-rather the main jet. I’ve done many many carbs and never yet had to replace one.

Once its running again, use non-oxygenated fuel and use a stabilizer such as the B&S stuff year round. The regular gas now is terrible on small engines.

Years ago when I worked fixing small engines, I cleaned out many carbs where the gas had turned to a gum and often rock-hard varnish. Carburetor cleaner spray tends to work if it’s only at the “gumming” level. It it approaches rock-hard varnish, an overnight soak in industrial strength carburetor cleaner was the only way to dissolve the clogging.

As Bing suggested, a multi-day soak in Seafoam may work for the difficult cases as well.

I think I’ll drain the gas out of my generator today. Rocketman


While working on the generator my 15-yr-old, just-beginning-to-learn friend asked “Could the non-starting be becasuse it’s low on oil?” Nah! And besides, there was plenty of oil. (You can see where this is going.)

Digging around the machine to find model number, etc., to get doc’s from the mfr’s, I see the little sticker: “This machine has low-oil protection circuit,and will not run with insufficient oil.” Hmmmm!

Look at the oil level again. Very low. What the heck??? Oh, yeah. Last time I looked at oil level, the machine had just been tipped toward that side. Hmmmm, again.

After I got the doc’s and got the parts I replaced the needle valve, a fancy filigree elastomer internal gasket, and the two plain paperish external gaskets. Did not replace main jet because the old one looked as clean as the new one (and I was afraid to push the old one hard enough to get it out).

And I changed the oil. About one oz. came out; almost a whole quart went in. Hmmm, indeed.

Put it all back together – one pull and she’s running like a champion.

So, it was, in fact, probably just too little oil in the crankcase. But cleaning the carb and the other stuff probably reduced the risk of future problems.

Thanks for your help.

Sta-Bil is great for such engines. The last time I attempted to start my Coleman/B&S generator I was successful on the first pull of the rope and the fuel is more than 3 years old but it was treated with Sta-Bil. After allowing it to run for about 15 minutes I shut it off and topped off the tank with fresh fuel with the additive. I have been test running the engine in that manner at least twice a year for the past 20 years. In all the years since buying that generator it was actually used less than 2 hours. But it’s ready to go.

Rod I know you like Sta-Bil and I do too. I just today started by B&S gen-set. I have not started it since the fall of 2010. I did not put anything in the gas. It had a 1/2 tank in it. It started on the second pull. I ran it for 5 hrs today (on that same gas) as I made my camper ready to go. I am on stand by for this hurricane. I know I dodged one this time. Just go’s to show you I sometimes would rather be lucky than good. Oh I did go and buy some Sta-Bil. Its stored in the camper with the oil for it. PS Do you think I should go and play the Lotto? LOL

Much of the advise given here depends on the size of the engine, the type of carburetor used (float or diaphragm) and the vintage of the engine…On generators, the fine springs that make up the RPM governor can not be damaged or assembled improperly…A single wire pulled from a wire brush makes a good tool for cleaning jets, air-bleeds, siphon tubes…

Today, many generators and snow-blowers have fuel shut-off valves and drain screws on the carburetor so you can turn off the fuel and drain the carb…

@art1966–I have a TroyBuilt generator and it does have a low oil level stop switch. I believe that this is done on generators because the generator may run for long periods of time with nobody around. This saves the motor when the oil becomes low.
Don’t feel bad. I completely overhauled a LawnBoy 2 stroke mower some years ago–rings, ignition points and condenser, and a new needle and seat in the carburetor. When I reassembled the motor and tried to start it–no luck. I checked for spark and had a nice fat blue spark. I removed the plug and poured a little bit of gasoline right into the engine. It started and died. I took the carburetor back apart, checked it thoroughly, reset the mixture at 2 1/2 turns and still no start. It finally dawned on me that when I was disassembling the mower, my three year old son was crawling around and so I poured the gasoline from the tank into a gasoline can. When I put gasoline in the tank, the mower started and ran just fine.

Um yeah, Been there. Some years ago I put a carb kit in my snow blower. No start. Back apart again same thing. Finally dawned on me I had the fuel shut off. Ran good after that. Sometimes we tell about these things and sometimes we don’t, depending on who we are trying to impress.