# Briggs 3hp overfilled with oil



## Bob DiGiacomo (Jan 15, 2009)

I have a small briggs that was hydrolocked with oil because someone put a quart and a half of oil in it. I drained the oil and got the mower running, but it is starving for gas just a little bit. The mower is like a year old and in really nice shape. It runs but has a very slight hesitation. I don't believe it is the carb because I switched up the carb and gas tank from another mower. Could the oil overfill cause this condition? The compression is 87psi. Thanks for any help or suggestions. Bob


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## indypower (Apr 8, 2009)

can you post the engine numbers?


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## Bob DiGiacomo (Jan 15, 2009)

Engine #

Briggs and stratton

9s502 3707 B1 07060751

Could there be left over oil on top of the piston fouling the plug slightly, even if I ran the mower for 15 min. straight? Please help I need to mow. Thanks


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## Bob DiGiacomo (Jan 15, 2009)

I thought I had this figured out by cleaning the head, but it is still not running right. It does not seem like a fuel problem the muffler is very slightly popping when it runs what is causing this? The plug is burning the right color. Please help!


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## Bob DiGiacomo (Jan 15, 2009)

Still need some help can't figure it out and don't know what to do? Please help.


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## LowRider (Dec 23, 2008)

have you tried adjusting governor?


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## Bob DiGiacomo (Jan 15, 2009)

I tried adjusting the springs but it made no difference. The governor is controlled by wind from the flywheel is that adjustable?


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## indypower (Apr 8, 2009)

Something is wrong with the briggs number you posted. Briggs site says invalid number.


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## Bob DiGiacomo (Jan 15, 2009)

You need to put a (0) Zero in front of the model number. I don't know why.

09s502 3707 B1 07060751


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## LowRider (Dec 23, 2008)

Bob DiGiacomo said:


> I tried adjusting the springs but it made no difference. The governor is controlled by wind from the flywheel is that adjustable?


Not familiar with how theres work. i know on Hondas you loosen the bolt on the governor and push it to full throttle till it stops then tighten bolt while its running of course.


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## geogrubb (Jul 28, 2006)

You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.
Here we go;

Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Check the intake tube to see if the “O” ring seal and plastic retainer are still on the intake tube, if so remove them and re-install them into the carb. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble), now with a small screwdriver pry out the main jet(carefully) and clean it, check the “O” ring on the main jet for damage, if it is damaged it must be replaced, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem(not necessary if the fuel tank was clean). Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo


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## Bob DiGiacomo (Jan 15, 2009)

Thanks Geo,
I was not sure if the diaphram would be bad on a 2 year old mower. It looks good to me by inspection. I will make the replacement and see what happens and let you know. Thanks again. Bob


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## hd4ou (Aug 25, 2009)

been my limited experience that when you remove the diaphragm from one of those carbs then its done..something about being out in the open and drying up just the slightest bit seems to distort them in the slightest way and they are not ever the same. when they are installed and are bolted in the bodies of the carb this keep it from shrinking or distorting.... i think Geo is right on track...


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## Bob DiGiacomo (Jan 15, 2009)

I put in the diaphram and it did not work. The engine still pops like it is running rich. Nothing changed with the new diaphram and the second carb cleaning. When I got the mower it was hydrolocked with oil, so I could not even pull the starter cord. I'm not sure if they got the mower to start when it was overfilled with oil or not? There is not a broken flywheel key and the compression is 87psi. What should I do now?


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## geogrubb (Jul 28, 2006)

Bob DiGiacomo said:


> I put in the diaphram and it did not work. The engine still pops like it is running rich. Nothing changed with the new diaphram and the second carb cleaning. When I got the mower it was hydrolocked with oil, so I could not even pull the starter cord. I'm not sure if they got the mower to start when it was overfilled with oil or not? There is not a broken flywheel key and the compression is 87psi. What should I do now?


I think I would remove the plug and muffler and flush everything with gas or carb cleaner to get rid of any remaining oil, just crank it over a bunch to try and clear it out, also the crankcase vent tube is probably full of oil. Have a good one. Geo


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## 30yearTech (Sep 14, 2006)

Just for grins, have a look at the flywheel key. A partially sheared key can cause this, and it would not be the first time I have seen a key sheared from hydro-lock. As long as the oil has been drained and refilled to proper level, this should not have any bearing on this. Check the intake manifold and make sure it's not loose or cracked.


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## Bob DiGiacomo (Jan 15, 2009)

I already pulled the flywheel and the key is good. I cleaned the entire head everything looked good. The spark plug is no longer getting sooty since the head cleaning. Intake has no cracks that I could see (plus I tightened the bolts). I will try to clean out the crankcase breather. Thanks


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## Bob DiGiacomo (Jan 15, 2009)

*Still need help*

I sprayed the crankcase vent tube with carb cleaner it did nothing. I checked the plastic intake manifold for cracks and found none and I made sure that the gasket on it was in excellent shape. I already had the muffler off and there is nothing clogging it. The engine runs perfectly fine, but just slightly pops every 5-8 seconds it is not a backfire. I'm thinking the oil overfill damaged the engine but what part? Would valves have something to do with this? Anyone know the valve gaps for this engine. Thanks again for all help thus far. Bob


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## phillipmc (Jan 27, 2008)

Being you have done all this, I would try just using it and see if it cleared up on its own. A lot of times it will if you have checked everything out first.


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## Bob DiGiacomo (Jan 15, 2009)

I let it run through a tank of gas and still nothing. If I spray starter fluid in the carb it evens out. I think it might be running lean. I put in a new diaphram in the carb. Would the o-ring on the main jet cause this problem (the muffler to slightly pop every 6-10 seconds?)


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## tractionroller (Nov 22, 2008)

Is the o-ring still in the back of the carb?


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## Bob DiGiacomo (Jan 15, 2009)

The o-ring is on the back of the carb. I'm pretty familiar with small engines. I have worked on about 6-8 other small mowers with similar engines and carb styles as this mower, but never had this type of problem. Is there any way to adjust the carb if it is running lean or rich?


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## justin3 (Apr 10, 2007)

Did you use an aftermarket diaphragm or a genuine Briggs one? Sounds like and air leak somewhere, carb to tank or carb to intake manifold. Could also be a restriction in the main jet.


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## dj722000 (Oct 29, 2008)

Sure one of the valves isnt stuck open or opened just a tiny bit? Sometimes this will cause this symtom.


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## Bob DiGiacomo (Jan 15, 2009)

It is genuine Briggs diaphram. I took the carb apart again gasket + diaphram are on in the right order no blockage in main jet and good o-rings. I am going to look at the valves next there is nothing left. Can someone tell me the valve clearance for this engine? Thanks


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## 30yearTech (Sep 14, 2006)

Sounds to me like normal for this type of engine. An air vane governor with a pulsa-prime carburetor. It's rare when they run perfectly smooth an occasional pop or sputter won't affect the operation of the engine.

Is it so bad that the engine rpm's constantly fluctuate? 
Are you getting black smoke out the exhaust?

If not I would say the engine is fine, there are no adjustments that can be made to this engines carburetor.

Valve clearance for this engine is Intake - .005 - .007 and Exhaust .007 - .009

Some Model Series System 2, System 3, System 4 have been built with .005 (.13) to .007 (.18) exhaust valve clearance. The breather on these engines are stamped on the inside surface.


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## Bob DiGiacomo (Jan 15, 2009)

30yr,

The engine runs fairly well. The rpms don't drop (much) when it pops. There is no smoke. The mower cuts grass fine, and doesn't come close to stalling. I want to fix this pop just because I have an interest in small engines. Not because I can't use the mower as it is. I will adjust the valves the intake was at about .004 when I checked it. I let you know what happens. Thanks


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## 30yearTech (Sep 14, 2006)

Bob DiGiacomo said:


> 30yr,
> 
> The engine runs fairly well. The rpms don't drop (much) when it pops. There is no smoke. The mower cuts grass fine, and doesn't come close to stalling. I want to fix this pop just because I have an interest in small engines. Not because I can't use the mower as it is. I will adjust the valves the intake was at about .004 when I checked it. I let you know what happens. Thanks


The point I was trying to make, is there may not be anything wrong. 

The type of governor on this engine coupled with the type of carburetor can sometimes and many times have a little hiccup periodically. It does not necessarily mean there is anything wrong with the engine. This is a pretty basic (and crude) set up, built cheap to sell cheap, and set to run lean for emissions. 

Best of Luck.... :thumbsup:


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## Bob DiGiacomo (Jan 15, 2009)

I did the valves and it made no noticeable improvement. I put on an older oil saturated air cleaner and it seems to have reduced the popping by about 40%. There is a new gasket between the carb and the air filter. I guess it is just the way it is.


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## hammerbot (Apr 24, 2010)

*pops like its running rich*

Could that mean incomplete combustion?

Leak in the head gasket from the overfill /over pressure?

Sound similar to issues I had before my head gasket completely blew out.

Just a thought.


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## dj722000 (Oct 29, 2008)

Well, if you put a old oil saturated filter back in then that tells me it is running lean as your reducing the air flow with an old oil saturated filter. Wow, say that ten times fast. LOL. I agree with 30yeartech. Probably not alot you can do with it and nothing is probably wrong. Just got under your skin a little. Just the way it wants to be. LOL


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## 30yearTech (Sep 14, 2006)

dj722000 said:


> Well, if you put a old oil saturated filter back in then that tells me it is running lean as your reducing the air flow with an old oil saturated filter. Wow, say that ten times fast. LOL. I agree with 30yeartech. Probably not alot you can do with it and nothing is probably wrong. Just got under your skin a little. Just the way it wants to be. LOL


If the filter were saturated with oil, reducing air induction into the engine, the resulting mixture would be "rich" not lean. A lean mix is more air then fuel, and rich means more fuel less air. :thumbsup:


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