OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 4hp Briggs and Stratton Quattro

I have a strange question regarding a Briggs and Stratton Quattro engine (the 4hp variety) sorry I don�t have the model type and code on me at the moment.

A guy dropped it around the back of my house and for some reason it got tipped up on its nose and leant against the wall. I was away for a few days and thought it was a little strange when I returned home.

The mower wouldn�t turn so I assume oil had worked its way to where it shouldn�t be. I took off the engine head and oil poured out everywhere. I also removed the valve chest cover to rid the excess oil. I left the mower tipped up with inlet valve open to rid the excess oil.

I fixed the obvious problem being the connector from the coil lead to the plug as it was loose and rusted. I also put on a new boot for good measure. It now has great spark.

So:
Great spark
Carby is clean with new diaphragm
Cleaned the exhaust as best as possible to remove excess carbon (unconventioned tapping with the hammer and then shaking out excess carbon)
Air Filter is clean and oiled
Coil re-gapped
Fixed starter cord as it was about to snap.
Valve clearances are pretty close to specs.
The bore was unmarked
Re-filled with second hand oil to the correct level (new oil goes in when the engine is right to go!)

Now all I can get is the odd pop from the exhaust with black smoke being emitted!

It has a deadmans bar that appears to be operating correctly.

I�ll post some photo�s tonight.

I am obviously missing something and would appreciate some help!

Does it have compression? If so, how much?

Usually, people throw away engines for a reason. It usually isn't a good reason by our standards, but it is nevertheless a reason. Until you have found it and fixed it, you are on borrowed time even if you get it to run. We need to get the model, type and code - I can't help you much without them - but I suggest you focus on two main possibilities.

1. The engine may have valve problems, hence little or no compression - that may be why it was scrapped.

2. The breather pipe will have filled with oil when it was tipped over. The amount of oil still in in the pipe may be enough to foul the spark plug.

I'll get those codes tonight for sure.

Yes the engine has compression - I havent measured it but its more than reasonable from my observations. Its only a couple of years old. I will put the gauge on tonight.

The previous owner assured me it was running but used to stop suddenly. I put that down to a loose connection on the spark plug which I have fixed. I was surpised it even started the HT lead clip was so loose.

Do you have a method to clear the breather pipe? I didnt think of that reason.

Thanks as usual.

If you can use a piece of tube to blow air through the breather pipe, you can clear the tube with a couple of puffs. I suggest you blow it downward into the valve chest if you can.

I'm doubtful that a Briggs engine actually stopped due to a loose plug lead, unless the lead literally fell off the spark plug. There may be a more subtle problem here, but if so, it should make itself known as you move forward.

You may have a sheared keyway throwing the timing out, remove the top nut and starter cup, it should be obviuos if that is the issue or not.

Hi Peter, I have found a couple of similarities with the Quattro 40's over the years, but they may just be a coincidence.
Check you're valve clearances and breather on the valve cover. Try removing the air snorkel (if it has one) and then try starting the engine. The remote filter/snorkel setups for some reason seem to restrict the breathability (if thats a word) of the engine.

Model � 10A902 Type 2164B1 Code 060226511
Excuse the last couple of numbers on the code as my pencil notes from last night smudged a little.
I cleared the breather pipe and a little excess oil came out but nothing notable.
I re-checked the valve clearances and nothing seemed too far out to cause concern.
Inlet - .12mm
Exhaust - .15mm
I checked the keyway and it deffinately isn�t sheared.
I washed the valve chest cover in petrol and made sure it was clear of excess oil. Could a faulty cover cause these symptoms?
It is the model with the foam air filter above the carby, so no snorkel.
After clearing the breather pipe things changed a little. I know get a louder pop and smoke seems to be backfiring around the carby area. Its like a light puff of smoke coming from the whole engine. FYI � the head gasket wasn�t damaged upon removal.
Not something I have encountered before.

First, some basics. The engine was built on 26 February, 2006. I think the last number in the Code is probably spurious and it should read 06022651. The plant which manufactured it is given as 51. Plant 51 seems to be an administrative center (identified as "TBS") at Briggs headquarters at Wauwatosa, Wisconsin, so I suspect you have an early production Chongqing engine. For one reason or another, Briggs does not seem to ever stamp the actual number for Chongqing (Plant 28) on engines made there for export. So far, they all seem to have Wauwatosa admin center numbers.

Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/18hszLXAnfBhU7y.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/msvtDR-K_ny7tH217FzoPu.pdf

You haven't posted a picture of the engine, but it seems to have a PulsaPrime carburetor as the only option. If yours does not have a primer, please say so.

Now, to the nitty gritty. The cover of the valve chest is also the crankcase breather valve, so it needs to be clean and clear. It has a flat phenolic/fibre flap valve held closed by a spring, which opens momentarily each time the piston moves down the bore. If it is clean, and the valve is not stuck, all should be well.

Because you have a primer carburetor, and those primers are rather prone to not working, one possible cause of not starting, is not having any cold starting enrichment. I suggest you put a small amount of petrol into the cylinder through the spark plug hole, and see if it then starts. If it does, your problem may be an inoperative primer.

I will put some pictures up tonight.

It is a pulsa prime carby.

Any thoughts on the smoke coming from the engine when trying to start. It comes out around the carby and exhaust. Well it appears to anyway. I checked the intake manifold and no cracks were present.

The fuel idea I didnt try as the plug was wet upon inspection. I will try your idea tonight.

Whoa, if the plug is wet and the spark is good, it is way too rich - don't prime it, either with the priming bulb or by putting fuel into the cylinder.

I think you will need to spin it over for a while with the spark plug removed, to evaporate the excess fuel currently in the cylinder. Then try following a normal cold start procedure: say three primes, controls in starting position, and give it a try. If the plug gets wet again, it will sound as if either the air cleaner is blocked, or the carburetor is flooding.

Did exactly as you indicated and no change. I swapped the carby for a known working one and still the same issue. I ended up taking the carby apart and it was full of oil.

For some reason oil was coming out the intake manifold and into the carby causing that puff of smoke I assume.

I am sensing catastrophic engine failure. Any thoughts?

Is that oil coming from the breather tube into the carburetor intake, or is it coming from the intake valve, backwards into the carburetor? Was there oil on the top of the piston when you took the cylinder head off?

You said the carburetor was full of oil. Where was the oil in the carburetor?

Does the engine have normal compression?

I am pretty sure it is coming backwards from the intake valve into the carby.
With the exception of the first time I took the head off there was no oil on top of the piston.

Compression was 100 psi.

The oil in the carby was in the throat of the carby when you look down with the air cleaner off. It also made its way to the diaphragm when I took it off.

I don't see how oil could come from the intake valve back to the carburetor unless there was oil in the combustion chamber, meaning it would be on top of the piston. Also, though less importantly, for substantial amounts of oil to get into the combustion chamber it would have to either come past the piston rings, or through the top of a broken piston. In either case, compression would be low.

Something you might try, is cleaning out the oil from the carburetor and inlet pipe, then disconnecting the breather pipe from the carburetor and spinning the engine several times with the starter. See if oil comes out of the breather pipe, and if oil finishes up in the carburetor. This should tell us for sure, where the oil is coming from.

Ok thanks
I messed up oil is in the combustion chamber because the plug is always oily when I take it out. Sorry about that. I tried your trick after replacing the breather cover with another and no oil was entering the carby either through the throat of the carby or from the breather tube.

So could the breather valve been at fault hence why I tried another

Still won't start though.

Sorry for all the questions

No problem about the questions - that is the whole purpose here.

So, since you changed the breather valve, has the oil stopped entering the combustion chamber?

Once the oil problem is fixed, we should be able to deal with the not starting problem quite easily.

Pete, i dont think you have an oil problem. The fact that the mower was left standing with the plug facing down is the reason for your oil problem. Grab a new plug or hot run that one in another mower to burn off the excess oil. Get some degreaser/carby cleaner and spray through the carby to clean your inlet and through the plug hole to clean the piston/bore. Pull the starter 10-20 times with no spark plug fitted and throttle control in the off position, so you dont get a fire, in order to discharge the excess. Refit plug and start the mower.

The combustion chamber oil problem has no pretty much gone after I used Bigted's idea however still nothing more than the odd pop of two when you try to start the engine. No more oil is entering the throat of the carby.

I should have noted earlier the starter rope sometimes gets difficult to pull like something is providing resistence. The starter itself is fine as i tried it on another mower.

Compression is ok so it should fire more with fuel in the plughole but it didnt. Still thinking........

Have you checked that you are getting a strong, consistent spark?

The symptoms are now a pretty good fit for a sheared flywheel key, resulting in grossly incorrect ignition timing, as rusty ute suggested earlier. Are you sure the key is OK? You need to remove the flywheel nut to be able to see it properly. You may even need to pull the flywheel off to check it definitively.

Yep I have good strong consistent spark. To be thorough I swapped a good known coil onto the mower and still the same result. (Just following the principle you noted about keeping spares of tested parts)

I took off the starter cup and the key appeared ok however I didnt take it off. I dont have a puller (will need to invest in one)

What is the best method to remove the flywheel without a flywheel puller. I have a 2 & 3 arm pullers which I use to remove blade bosses but I dont think my big puller will fit.