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Briggs and Stratton coil UPDATE success !

Charles in Aus.

Charles in Aus.

Well-known Member
My back let me work on the mower today , I had no choice but to dig a deep hole on the weekend , surprisingly I am better off for it .
It was the flywheel key after all . Full marks and credit to those that mentioned it as a possible cause , I am indebted to you . :)
The replacement cost me one dollar and it didn't take long to replace at all . Now thanks to all the other suggestions the coil is nice and bright, gap to flywheel adjusted and kill switch working nicely with new wire .
Hopefully this photo will show the sheared key and position of the flywheel .
mvphoto73823.jpg

Some cable adjustments and mine and the neighbour's lawns were cut nicely this afternoon.
:D
 
That's really good to know. I have a B&S motor on my leaf blower that's real fussy about starting; I might just pull the flywheel and check the key.
 
Congratulations glad to hear alls well, the coils nice n bright, and you have a good spark now...

John T
 
Wow! That's really sheared, it must have taken quite a hit!

Usually they are only partially sheared, even that is enough to stop one from running.
 
A sure sign of a partially sheared key is when you pull the rope and it wants to kick back and yank the rope out of your fingers. Yes it hurts. The reason that the key shears is a sudden stop of the blade.Then you have the rotating mass of the flywheel that has energy to twist on the crank. I have seen them shear only a few degrees or like yours a lot. A key that is sheared only half way will advance the flywheel and ignition timing. That is what makes it kick back and yank the rope out of your hands and makes them hard starting. I have seen cases where it can shear the key, and bend the crankshaft and break the blade adapter.
 
Charles in Aus,

I am glade you got it going. With all
those shiney part, it had to start right?

A sheared key will stop the engine from
running, but will not effect the spark.

If the flywheel is turning it will spark
out of time, hence a no start.

GUIDO.
 

That is odd Guido . The first thing I did was put a spark indicator onto the lead when it wouldn't start . There was nothing , no matter how hard I pulled , which was why I suspected the coil . Perhaps my old eyes are worse than I thought :(
But it runs now and that's what counts .

Continuing on its cursed condition it now skips a bit when I engage the self propelling gear box , it grinds a bit then engages but doesn't seem to go as fast as it did and gets bogged down in longer grass .
 
Charles in Aus.

A sheared key is a mechanical failure, AS
I said, it does NOT affect the spark.

When looking for spark, here is what I
use.

I see SOOO MANY people laying the spark
plugs on the engine .
Every time they
pull the rope, the plug moves...hilarious!
This $1 clamp works everytime!.
I got 2 of
the big one for that dollar. AND I can see
the spark at the plug at the same time,


GUIDO.
 
(quoted from post at 14:39:25 04/20/21) Charles in Aus.

A sheared key is a mechanical failure, AS
I said, it does NOT affect the spark.

When looking for spark, here is what I
use.

I see SOOO MANY people laying the spark
plugs on the engine .
Every time they
pull the rope, the plug moves...hilarious!
This $1 clamp works everytime!.
I got 2 of
the big one for that dollar. AND I can see
the spark at the plug at the same time,


GUIDO.
Click to expand...
eems most posters look to the unknown/mysterious things first, instead of the simple. So often!
 
(quoted from post at 00:43:34 04/19/21)
Some cable adjustments and mine and the neighbour's lawns were cut nicely this afternoon.
:D
Click to expand...

Well Charles, the best way to test that mower now is to come over and mow my lawn once a week for the rest of the year. You can see if the new key holds up. lol
 
Charles in Aus.

You can check the ignition strength with that too. Just gap the plug to 1/4 IN or so. A good ignition
module WILL jump that gap. You will also SEE if the spark is going to ground around the plug end too!,

Guido.
 
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