Export thread

Hi.
My problem is old B&S 3.5 HP push mower engine.
It hasn't been used for most of the summer, because in the beginning of the summer it started to
act up. It starts with the first pull, runs 1-3 seconds with high-ish revs and dies.
I checked and adjusted the valves (probably not done in the last 10 years if ever) and changed the
diaphragm, and in the process cleaned the carburettor a bit.

What could cause that dying?
Leak between the gas tank and the (tank-mounted) carburettor?
Somehow damaged diaphragm (or mis-pre-loaded)?
Leaking or mis-adjusted valves?
(Still) dirty carburettor?
I guess not the tank cap - it probably would run longer then? Minutes?

The gas tank was emptied during the cleaning (and mixed with about a gallon of new gas).

The engine is 1973 manufactured 92902, and I used it (on another mower frame) wha I was a teen (now 51).
It's probably not worth much money, but it has personal value to me, and it's also kinda cool to have
an almost-half-of-a-century-old B&S in active use.

Oh, forgot, the carburettor is Pulsa-Jet Automatic Choke.

Replace air filter and spark plug.

http://www.briggsandstratton.com/~/...on_troubleshooting_detail_reference_guide.pdf see failure tables #8 & #9 won't stay running

Total cleaning of the fuel system, and probably time to "tune up" or replace the ignition system.... Those points can be troublesome......

@mechanic mark: Spark plug ans air filter were changed last year and there is very little electricity to adjust - just the airgap, and it looked good.

@Fish: I'll do that.

If your system does have points, I would suggest that you just clip the wires to the points under the flywheel, and install a newer electronic coil, and be done with it. An old time mower shop likely has a bucket full of old good coils....Cheap.....

im still a bit new to engines as only playing with them foe 2 years and prob only done 10 or sow mowers but will say one of my last and one of my first mowers were briggs engines and both where problems with condenser and points and most sets can be bought from ebay for ｣5 for a new set the last mower i had sparked but did not run took a chance as was told you cant really test a condenser un less got special test stuff replaced and mower runs very good and went to a good home prob will run for the next 20 years all for ｣5 and a bit of carb cleaner

Ok......... Not sure what you said, but OK....

im still a bit new to engines as only playing with them for 2 years and prob only done 10 or more mowers but will say one of my last and one of my first mowers were briggs engines very old a hayter 12 inch cut 1979 point problem and both where problems with condenser and points and most sets for briggs engines sets can be bought from ebay for £5 for a new set the last mower i had sparked but did not run took a chance as was told you cant really test a condenser unless got special test stuff replaced points and condenser and mower runs very good it went to a good home prob will run for the next 20 years all for £5 and a bit of carb cleaner

if you got a condenser and points replace for new before fault finding as when condensers get old and hot can cause many problems and for the cost of a few pence the first place i would start or as said change to electronic

OK, I guess it might be the monetary thing.......

So are you saying that buying the cheapo Chinese points/condensers are good enough, with a squirt of carb cleaner?

And what is L 5 worth in American? Euros? I never got that thing yet. So you are all on the Euro thing, or what?
L 5 means 5 pounds????? gawd I will try and find you an electronic coil "used" in my shop, and mail it to you, so you can open a
new horizon...... I will put it in my e-bay store, and sell it real cheap.... What are the model/type numbers?

My engine (92902) has (composite) magnetron. The only adjustment is air gap and it's "one piece" - there is nothing replaceable except the whole unit. The spark looks fine, so I don't think the problem is there. It also starts with one pull, but dies right after that (1-3 seconds).

But for those that have points: a car-made capacitor with wowen terminal(s) is usually better. The vibrations tend to wear the contact thread to break. Also the car-made capacitors bear cold weather (frost in winter when in storage) usually better. Then again, the function of the capacitor is to stop arcing between the contacts. The quality (or even capacity) is not very important. Too small capacity or missing capacitor just make too long spark and wears the points fast.

BTW: about the currency rates, I often use this: XE Currency Converter - Live Rates
Now it says (GBP = £):
1.00 GBP = 1.66955 USD
and
1.00 EUR = 1.33999 USD

So 5.00 GBP = 8.34775 USD

There are some countries in EU that don't belong to the monetary unit (euro) but have their own currencies.
Great Britain is one of them, Sweden is another.

Then take apart your fuel system again, and look closely at the tank, and any rust, they make hole and are porous and leak a lot.

no china cheap parts are not a good items but will last for a few years and generally better than a 35 year old well used part and as most mowers are not worth 100s pounds or bucks

corner do not have to be cut to make it worth while fixing but you have to take in to account the price for a working mower if its £30 aprox 50 bucks you are not going to get a mustang for the price of a banger

So in Great Britain, can either currency be used? Is it required to accept either currency? The Euro is optional?

As far as the engine, it has the electronic coil? Can you put up a few pics????

Fish said:

So in Great Britain, can either currency be used? Is it required to accept either currency? The Euro is optional?

As far as the engine, it has the electronic coil? Can you put up a few pics????

Click to expand...

I haven't taken any pics, but found some in the net:

The coil

Here's the explosion picture
I just don't think there is a breaker. At least the manual "270962 Single Cylinder L-Head BRIGGS & STRATTON.pdf" doesn't mention them.

Anything "pre" 1983 from Briggs used points. I'll bow out and let the other guys help you.

Fish said:

Anything "pre" 1983 from Briggs used points. I'll bow out and let the other guys help you.

Click to expand...

I got curious. I removed the flywheel and... there they were - points!

What's the cylindrical part that has the other point on its end?
Kind of looks like capacitor, but then not. And capacitor should be parallel to the breaker.

turboscrew said:

I got curious. I removed the flywheel and... there they were - points!

What's the cylindrical part that has the other point on its end?
Kind of looks like capacitor, but then not. And capacitor should be parallel to the breaker.

View attachment 22772

Click to expand...

Wow!!!! I came back!!!!

There are several dozen guys here "panting" to help you, I am sure!!!!!

Fish said:

There are several dozen guys here "panting" to help you, I am sure!!!!!

Click to expand...

I was waiting for you to fix his so I could fix mine.

I have one does the same thing so can you hurry up and tell him what's wrong.

Thank you

Carscw said:

I was waiting for you to fix his so I could fix mine.

I have one does the same thing so can you hurry up and tell him what's wrong.

Thank you

Click to expand...

Stop panting....

Sounds like a dirty carb to me. My push mower would crank up to to full rpms and then immediately die so I took the carb off the engine and cleaned every jet or opening thoroughly and replaced all the gaskets. It's working fine now. If you took the nut off the bowl and just cleaned it the gasket could have degraded and clogged the main jet too.

According to the explosion picture the cylindrical part IS a capacitor.
That kind of thing you'll never find in any electronics shop. Very special part.

Also, can anyone tell what kind of screws are the number 10s in the explosion picture?
I had to put the mowet in with a hurry, when it started to rain. I forgot that I had the screws on top of the mower, and
now they are lying somewhere on the ground. I'm not very optimistic about ever finding them.
(Yes, intake valve clearance was fine, but exhaust valve clearance was too big - almost 0.010".)
Which threads (inch or mm) should it have? What size?

Looks like the spare part number nowadays is 691666.

I've now cleaned the carburettor twice. I also hope that I preloaded the diaphragm right (I'm a Finn and I'm not sure what
"over center" means in "Move choke plate to an over center position").

Well, you are likely talking about the "condenser" of the "points and condenser" set, which is still readily available, or you could just simplify things and replace the whole ignition system with on of the newer used "electronic" coils, but that was a suggestion from a while back...., So you wouldn't have to pull the flywheel, and then we would have the new nasty variable of wondering if you torqued the flywheel back down tight enough.

But if you refuse to listen to folks trying to help, that is fine. You could replace the points/cond, or not, or just put on a used cheap electronic coil, or not, just keep making posts about everything else....

You may be right, and it has nothing to do with "ignition"..... If so, great.

Sorry, I didn't mean to be stubborn, but the first advice was to make sure that the carburettot is clean. I did take a second cleaning session.
If there's something wrong with the ignition, would it start with first pull each time?
I'm also no so sure I can get the ignition parts very easily around where I live.

The spark looks good when I take the spark plug out, keep it against the engine and pull from the chord.

And another thing: After trials, the spark plug is always dry.

Yesss, my wife found the screws - the work can continue...

I put it together and... IT RUNS AGAIN!
Could it have been the broken valve cover gasket (made a new one from Armstrong N-8094 material).
Could there have been a carburetor leak through the breather tube?
If not, then it had to be some dirt left in the carburetor.

Thanks guys!

BTW: should I put "[solved]" in the heading or something?
Any way of giving points? (Haven't seen any.)

turboscrew said:

I put it together and... IT RUNS AGAIN! Could it have been the broken valve cover gasket (made a new one from Armstrong N-8094 material). Could there have been a carburetor leak through the breather tube? If not, then it had to be some dirt left in the carburetor. Thanks guys! BTW: should I put "[solved]" in the heading or something? Any way of giving points? (Haven't seen any.)

Click to expand...

Glad you got it going.
No points here.

great. glad you got it going. did you clean those points while you had it apart? Come on, be honest now. Anyone in their right mind would have done so, when he went to all of that work to discover that he had "points".....

Broken valve cover gasket???

Carb leak through breather tube? Some dirt left in the carb? Wow, those mysteries will continue to confound us all.......

Either way, you have it running again...

No, I didn't touch the points. They looked pretty good (I wonder why?).
I tried to take photos of them using macro, but I should have aimed with the display instead of the view finder.
In macro use the view finder of Canon A590 is terribly off. The points didn't show in the pictures.

I must have broken the valve cover gasket when I measured the valve clearances.
The breather tube goes from the "box" under the valve cover (that's what the documents call it) to carburetor.

Anyway, what I did was making a new gasket and re-cleaned the carburetor with carburetor cleaning spray.

[edit]
This is probably the best picture of the points

Dang, you got some nasty looking points!!!! In the old days, shops offered a "tuneup" which was an oil/filter/plug change, and a
cleaning and adjusting of the points, something done yearly, or at least "bi-annually". But when the electronic ignitions came
about, same with automobiles, it was just the oil/filter/plug change. But if you really are happy with it, then great.... I'll back out and let you decide what fixed your problem.... When you have burned/pitted points, you will get all kinds of different symptoms, which change with the barometric pressures and humidity, but no matter, you are good to go, glad to hear it.

It doesn't show in the picture (that's why I tried using the macro) but the contact faces of the points
were shiny and I didn't notice any "peaks" (don't know any better English word for the spark-caused
"little mountains" that tend to build up on one of the points' surfaces).

My father must have changed them before I got the engine. It's bee in my active use for about 5 years,
and before that almost 10 years on a storage room shelf.

I guess it's not too easy to find new points here. They don't look very common.
One of the points is attached on the end of the capacitor. I guess adjusting them
(no gap measure known to me) is done by adjusting the mounting position of the capacitor.

Last year I bought the last diaphragm for my carb type they had in the local B&S service.
For the points I probably have to wait a month or two. Well there is no B&S service in my home town,
but there's one in Tampere - the biggest (population about 300 000) village in Finland.
Tampere is the second biggest city in Finland and still in the whole sub-region
(Pirkanmaa - 5,586.66 sq mi, half a million people) no one sells 2-component polyurethane either!

Dang, if you get it broken down to the points/cond.... At least buff them with sandpaper and re-set the gap!!!!! Your engine will start and run a lot new carb diaphrams would make the units start and run better, but without changing them out, the units will still start and run. I am not trying to fight with you, but most of the folks here with any sense would tell you, if you had the flywheel off of a 35 year old engine, you should at least clean up and adjust the points, or even better, pop on a good used
electronic coil for $10, and never worry about the ignition again.....

Let me know, if I have a good coil laying about, I'll ship it to you, you just pay for shipping!!!!

How wide should the point gap be?
At least 270962 Single Cylinder L-Head BRIGGS & STRATTON.pdf doesn't say anything about the points.

The same in all engines?! Cool!

The contact point gap for non-electronic ignition systems (typically engines manufactured BEFORE 1983) is .020"

Click to expand...

Also, interesting page otherwise too!

Thanks, Fish!