B&S Engine Q

Don't know a newsgroup for it. However the most likely cause is the carb. There will not be a "factory" setting for it though (there's just the rule of thumb of 1 1/2 turns out from bottom on the older carbs, that's just to get you started and then fine tune from there).

The fact is the most likely cause of your problem is a clogged idle circuit. The engine will throttle down but with the idle circuit stopped up it'll start to die. Thus the governor will rev it up to prevent it from dying. Then the cycle starts again.

With a engine that new the chances of having a high speed adjustment are slim to none. There's even some that don't have a idle adjustment but most likely it does. Also likely on that new a Briggs is that the idle adjustment is actually a idle air adjustment and works backwards for the standard idle adjustment.

It just depends on which carb it has on it. The best I can do without knowing what carb it has is to say that a idle air adjustment will be near the mounting flange of the carb and a standard idle mixture adjustment will be on the side of the carb. That's if it has a standard float carb. Updraft carbs and several other types change the rules.

Wayne Cook Shamrock, TX

Yeah, what he said! ;-)

If the engine is one of the newer overhead valve B&S engines there is no high speed adjustment. I have a generator with a 13 HP overhead B&S and it runs poorly without a load. Loaded, it runs fine so I don't worry about it. It has a fixed jet carb so unless I try drill the jets or some other unapproved method of repair it will not get any better anyway. Greg

Has this generator been standing unused for a while? If so, a carburettor problem would be my first bet. Remove the bowl and look for crud inside. Anything solid can intermittently block the jet, causing the variations in speed.

Chris

I have not gone outside to look at the carb itself, but the owners manual that came with the generator's engine describes an "idle mixture valve with limiter" (a screw you can turn) and an idle speed screw. I'm not sure if either of those needs adjustment. This is a fixed speed engine which should maintain 3600 RPM. It runs fine at "idle" - i.e. no load. When it's loaded its speed surges / oscillates

- lights dim and bright, etc.

It sounds like my best bet would be to clean the gum out of the carbeurator, but short of full disassembly, I'm not sure where to squirt carb cleaner in this one. My usual quick Spring cleaning of fussy carbs on my weed whackers is to remove the needle screws and squirt carb cleaner into the jet holes. This makes them run well for the season. I'm not sure where to squirt the carb cleaner to do a quick cleaning on this Briggs carb although once I remove the air cleaner and bowl, I may see passages I can try. I haven't gotten that far yet.

There is no high speed adjustment on this one from what is indicated in the owners manual, but I'm not sure if it's an overhead valve engine. It's an 8 HP Model 197400 (Specfically Model 197412, Type

1144-E1, Code 9912081A)

Mine's the reverse. Without load it "idles" at 3600 rpm fine, but even after running for an hour, if a 1 KW load is on it, it surges. At 500 watts load it runs OK.

RWL

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RWL wrote in news: snipped-for-privacy@4ax.com:

sounds more like a problem in the govenor rather than the carb. Are the fins clean on the flywheel? Remove the flywheel cover, clean the flywheel fins, govenor blade and oil the pivot for it. I would also oil the idler linkage for it and check for binding.

Ok.

As one poster stated it could be the governor in this case. However it still could be the carb. In this case it's the high speed jet that's out and since it's most likely a fixed jet then the most likely cause it that it's stopped up. Since we still don't know which carb it is then we'll go with the most common for the newer engines again. You'll need to shut the fuel off from the tank (if there's a valve then your great, if not then carefully use a pair of vise grips or similar to pinch off the hose, be careful not to tear the hose, preferably you use a pair of pliers made for this but few people have them).

Then depending on the engine it may be easier to pull the whole carb or if you can get to it just pull the float bowl off. The screw that holds the float bowl on will most likely have the jet in it (there are some carbs where the jet is in the side of the post that the screw goes into, and others where it's up inside the post but they're less common). If the jet's in the screw then you need a very fine wire to clean it out. My preferred tool is a strand from a old lawn mower kill cable. The wire is small enough to fit in any jet and stiff enough to work. Spray the jet backward with carb cleaner and blow out with air in both directions. Clean the crud out of the float bowl while it's off. Spray some cleaner up the post of the carb and if you took it off look for a small hole off to the side inside the post. This will be the idle circuit. Try and spray through it as well while watching for cleaner to come out the small holes in the side of the carb near the butterfly.

If you left the carb on then hopefully the float bowl top gasket stayed in place on the carb itself. If not it can be a real trick to get the bowl back on with the carb still on the engine due to gravity pulling the gasket down while you're doing it. For this reason it's often easier to just pull the carb (it's fairly easy to do on the newer carbs). If you do pull the carb be darn sure to make note of where all the linkages go before pulling it. There will likely be more than one hole for each and it can be hard to tell which is the right one once the carb is off (experience helps here but your trying to gain experience on this one).

Once back together try it out. Use your finger to pull the throttle shaft against the idle screw. If the engine dies or runs rough then the idle circuit needs adjusting (or possibly the idle speed screw is set to low but that's not likely if you didn't move it). If you can't get it to idle with the available movement of the screw then pull the plastic stop cover off the screw and try some more movement. The idle air screws are trickier to adjust than the old idle mixture screws so some patients may be in order. Once it idles properly then you can try it out under load and see if it still hunts. At that point it's likely the governor.

One other point that I almost forgot. It may just be that the throttle shaft in the carb is stiff which will cause the governor to overshoot when it tries to adjust. Before going through the above reach in there and move the throttle shaft. If it doesn't move freely and return easily to the previous position with the spring pressure then the shaft is stiff. Spraying some cleaner and then light oil on it may fix the problem.

Wayne Cook Shamrock, TX

Before you tear down the carb as other have mentioned, look at the linkage between the governor and carb. The small steel rod needs to have a little bitty spring wrapped around it. If not there, you need one, and if there, make sure both ends are hooked. Depending on if your engine has always had this problem, the governor spring may be located incorrectly. If you find the governor return spring, you should find two holes on the linkage where you can attach it. One close to the pivot, and one farther away from the pivot. The one near the pivot is for wide response engines, like lawnmowers, and the one farther away is for generator use. It makes the governor "stiffer" when sprung form there. But if you generator worked fine before and slowly went out, this isn't the problem. Also, how old is your gas in the generator? Old gas can cause this problem as well. Failing all of that, clean the carb as Wayne described. The symptoms you describe also match a partially blocked main jet or a low float level.

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That is very good advice. DAMHIKT.

With the advent of low cost digital cameras, I tend to take disassembly pictures of things I'm not sure I could put back together blindfolded.

Wes

Sorry to burst you bubble, but B&S does not use an air vane governor on anything over around 3-1/2 HP! Greg

I would bet that is your answer. Some passage or jet is plugged or restricted so a carb cleaning is in order. Greg

Carb cleaner and compressed air generously applied did wonders on the lawn mower carb after second son left it with stale gas for three years. Gerry :-)} London, Canada

I had a chance to work on it Saturday afternoon, prior to receiving most of the messages.

I drained the old fuel and put fresh fuel in with Sea Foam brand fuel preservative. It ran better under load than it had, but was still seeking a little with two high intensity shop lights hooked to its 110 V outlets.

I then cleaned the carb while attached to the engine. It has a bowl and when you remove the nut on the bottom, it exposes a plastic float with a brass needle. The tip of the needle is coated with a reddish brown coating that looked to me like it should be there. It didn't wipe off with carb cleaner. I shot carb cleaner in all the passages I could spot, and had brown colored gunk running out the carb.

After reassembly it ran better still. No perceptible seeking when the two halogen lights were hooked up. Now it was time for the disaster drill.

I cobbled up a patch cable to backfeed 220 through the welder's outlet and shut off the main breaker to the house, and all the individual breakers in the box. I particularly wanted to know if it would handle the 1.5 HP submersible pump for the well. It managed to run the pump and fill the tank, but the generator speed oscillated wildly when the pump was running, so the problem isn't completely solved.

While trying out different positions for the governor return spring, I managed to stretch it. I need to replace that spring since now the generator runs at 55 Hz, putting out 98 V without load and about

107-109V when a light is connected. Prior to accidentally stretching the spring, it idled at 60 Hz and with a light load put out something over 110 V and about 215V IIRC.

Not sure if the spring for my genny is a commodity item that a lawn mower shop would have or whether I'm going to have to really hunt for a replacement.

I probably need to replace that spring before I can do any further evaluation of how this thing is working.

BTW Wayne, in reading your comments from two of your posts, the carbeurator has a horizontal intake. The idle air mixture screw allows access to a passage, but it's a fixed screw with no apparent adjustment ability. It's just a square / blunt ended brass screw. Removing the carb may not be so easy. It's held in place with two studs that have a male star pattern on the end. I don't have a female star shaped wrench. I hope this helps to identify the type of carb that's on this genny.

Thanks for all the other comments too. Probably not a whole lot more I can do till I find a replacement spring.

RWL

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Sounds right. You should remove the screw holding the float bowl again and look closely at it. It's going to have the main jet and most people miss that fact when trying to clean a carb. The tip of the needle will be either metal or rubber. Sounds like yours is rubber.

It'll depend on whether they stock the springs or not. You will need the exact right spring for that model engine. Be sure to right down the model, code, and spec number off the engine itself (generator model number doesn't mean much when ordering engine parts).

Definitely.

Hmm. You're almost describing two different brand engines here. The fixed idle jet has been a main stay of Techumseh for a good while now. But it's located next to the flange of the float bowl. It has a hollow screw which is the fixed idle jet. The male star headed studs are also found on some Techumseh engines but not on the old style Techumseh carb with a nut holding the float bowl on. They're used on the newer ones with a aluminum extrusion carb that has a wire clip holding the plastic float bowl on. This type also has a blunt end screw in the side of the float bowl with a spring behind it. The spring holds the main jet (plastic piece) in place against a o-ring. Normal failure mode is the o-ring gets soft and mashes closed cutting off the main jet.

Briggs uses studs to hold the new style Walbro carbs on. But I'm trying to remember one that has the male star head on it. Instead there's a recessed hex head buried in the carb that takes a metric deep socket to loosen.

Is the star a 6 point or 12 point? If 6 point then it'll be a male torx head. If 12 point then it just takes a standard 12 point socket (though those are hard to find that small).

The Walbro carbs have the idle air mixture adjustment near the output flange of the carb. The idle speed is near or on the throttle shaft (I can't remember which the Walbro's use at the moment).

Ok. I just did some searching and based on what I saw there's a really good chance that you've got a Techumseh engine there. What model is your compressor? See if you can find a model number on the engine itself as well. Even easier would be if you could get some pictures so I can see what it looks like.

The spring is critical alright. However you might be able to tweak it a little and get the generator running closer to proper rpm. There's two ways that can happen depending on engine and linkage design. Nearly every generator I've ever worked on has a adjustment somewhere to set the rpm of the generator. If for some reason (as in the engineers had there head you know where) there's not one on yours then it might be possible to bend the hook at the end of the spring so as to make the spring a little shorter. There's at least a chance that this will get the generator running properly. It might be a little more or less sensitive to load with the spring like this but it should run at the proper rpm.

Wayne Cook Shamrock, TX

"Greg O" wrote in news: snipped-for-privacy@corp.supernews.com:

Good. I haven't had anything over 5 hp apart, thankfully. It was just a suggestion.

Check your mailbox for the Photos Wayne. I didn't post them to the dropbox since I don't remember how and it seems you're the only one who recognizes this B&S carb.

RWL

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I just got through answering it. Sorry for the delay. It's been a rather rough day.

Wayne Cook Shamrock, TX