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briggs carb, do they wear out?

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#1 farmer john OFFLINE  

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Posted May 03, 2015 - 09:32 PM

I have a not so old briggs on a tiller, the carb is the type that is attached to the gas tank, I have taken it off twice, cleaned it up, put in a new diaphram, it runs then dies after 2 minutes, now it will not go on full throttle and I have to run 1/2 choke, I have never had this tiller running correctly and neither did the guy I bought it from, if it had a float I would say it was setup wrong but theres no float on this b&%#h, its sitting in the garden buried where it died, boy is it peaving me off, I keep looking at my ariens rocket with no motor on it, maybe I should put my efforts into that, I just hate being beaten by a briggs, not a fan of the new stuff
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#2 JBRamsey ONLINE  

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Posted May 03, 2015 - 09:36 PM

By not so old, is it not so old that it has a primer pump on it? If so, it may be cracked and sucking air.

Also, check your fuel tank. Take it off and flush it out. You may have some trash in it.
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#3 classic OFFLINE  

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Posted May 03, 2015 - 09:39 PM

Did you remove the suction tube from the carburetor? Sometimes the tube gets gummed up and the screen at the bottom of the tube can get restricted. The tube is brass and might be threaded into the carb body. Some are just pressed in. Be careful not to break it off if you decide to remove it.
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#4 boyscout862 ONLINE  

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Posted May 03, 2015 - 09:42 PM

You need to find the right manual in our manuals section and follow it. Those carbs can be frustrating but following the manual ends up easier in the long run. Good Luck, Rick

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#5 trowel OFFLINE  



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Posted May 03, 2015 - 09:45 PM

If anything, Classic is right about the screen, try that.

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#6 bbuckler ONLINE  

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Posted May 03, 2015 - 09:49 PM

By not so old, is it not so old that it has a primer pump on it? If so, it may be cracked and sucking air.

Also, check your fuel tank. Take it off and flush it out. You may have some trash in it.

Sounds like a pulsajet carb shouldn't be a primer bulb.

Like Classic said check those tubes . also what does the intake gasket look like ?

Edited by bbuckler, May 03, 2015 - 09:52 PM.

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#7 Bruce Dorsi OFFLINE  

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Posted May 04, 2015 - 06:39 AM

My first thought is that you may have an ignition problem.  ...Have you checked for spark immediately after the engine dies out?


Which B&S engine?  ....I'm assuming an older 3hp, 4hp, or 5hp horizontal crankshaft.  ....Let us know what model you have.


If so, those B&S carbs are simple, and rarely wear out. .....The only place wear can occur is where the throttle shaft goes through the carb body.


Is the carb diaphragm spring installed correctly?  ....The spring goes into the carb body first, then the spring cap with the smooth side out, then the diaphragm, then the cover.  ....If the spring is on the wrong side of the diaphragm, it can run, but will not pump fuel properly.


Next, remove the hex nut from the carb body.  ....This is the hex that surrounds the needle valve.  .....Under the hex nut, there is a brass jet which sometimes loosens up, changing the adjustment and stopping fuel flow while the engine is running. 


Remove the brass jet with a screwdriver having a wide tip, to prevent messing up the brass jet.  .....Under the brass jet, there are 2 small holes in the carb body which need to be clean (compressed air works best).  .....Clean & re-install the brass jet and tighten it, making sure you don't mess up the brass. 


Unscrew the needle valve a few turns from the hex nut.  .....Re-install the hex nut with its gasket, and tighten that.  .....Tighten the needle valve until it lightly seats against the brass jet, and then unscrew the needle valve 1-1/2 turns.  ....This setting will be close enough to get the engine started.  ....Final adjustment is made with the engine running.


As others have already said, there are two fuel pipes which extend from the carb body into the tank.  ....At the lower end of these tubes there are fine screens to filter the fuel.  ...Often these screens get "lint" or crud on them, and need to be cleaned.  ....Some of these screen housings have a check valve built into them.  ....While it is not common, sometimes these tubes can crack, creating an air leak which prevents suction up the tube.


The long fuel tube brings fuel up to the reservoir in the tank, where the short tube then brings fuel up to the carb.  ....A lot of times, water can collect in this reservoir, and the engine will not run properly (if at all), even though the fuel in the tank looks clean.


On many of these engines, vibration causes the 2 bolts holding the carb to the engine to loosen.  ...If there is a vacuum leak here from a loose carb or faulty gasket, the engine will be hard starting or die out.


There is always a cause for the problem.  .....Providing more information helps get more accurate help.  .....Does the engine restart immediately after it dies out?  ...Does it have to sit for awhile and then re-starts easily? .....Do you have to pull the starter many times before it starts?  ....Does it have a good, strong spark?  ....Does it have good compression?

Edited by Bruce Dorsi, May 04, 2015 - 06:44 AM.

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#8 crittersf1 OFFLINE  


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Posted May 04, 2015 - 11:27 AM

They can be persnickety.

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#9 thom OFFLINE  

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Posted May 04, 2015 - 08:15 PM

I think that even if all is well with the carb sometimes the engine will not draw a fuel charge into the cylinder due to a non-sealing exhaust valve. When the intake stroke happens if the exhaust valve is not sealing, air will be drawn in thru the exhaust port and muffler . The "plain" air is easier to draw that the denser, heavier air and fuel mixture.I have a 4HP Briggs that seems to have the problem now . I have cleaned the carb, and replaced the diaphram and the engine still will not run. A check of the ex valve is next. Depending on the muffler style you can possibly hold a piece of paper to the muffler and see if there is any "draw" on the exhaust side.

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#10 CraftsmanGT OFFLINE  

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Posted May 04, 2015 - 11:58 PM

Sounds like a Pulsa-Prime carb. If the primer even has a tiny hole or rip it will not run. Also check the mating surface between the carb and tank to make sure neither is warped
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#11 farmer john OFFLINE  

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Posted May 05, 2015 - 07:04 AM

thanks all; took it all apart, it all looked clean, but I cleaned it again, however this it when I put it back together I sprayed liquid form a gasket on all mated surfaces, it is now purring like a kitten (for 15 minutes, not under load)we will find out later today if all is well, thanks one and all for your thoughts on this matter. farmer john
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