Old 3.5 HP B&S runs a few seconds and dies

[clemsonnum1]

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.

 

[turboscrew]

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").

 

[Fish]

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.

 

[turboscrew]

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.

 

[turboscrew]

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

 

[turboscrew]

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.)

 

[Carscw]

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.)

Glad you got it going.
No points here.

 

[Fish]

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...

 

[turboscrew]

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

 

[Fish]

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.