Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

Any ideas?

cheers

Jules

"Jules" wrote in message
news

Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

No earth at the switch resulting in no short circuit to earth on the LT side
to stop engine

"R" wrote in message
...

"Jules" wrote in message
news

Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for
spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which
goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

No earth at the switch resulting in no short circuit to earth on the LT
side to stop engine


He's tried shorting to ground already however.
I'd say the other end of the wire (magneto end) has become disconnected, or
that there is an internal break in it.

"Jules" wrote in message
news

Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

Any ideas?


If there's a bolt close to the plug, I'd be tempted to cut a strip of metal
which is shaped and of sufficient length to short out the plug when pushed
onto it, as seen in many old lawn mowers.

On May 14, 6:20*am, "R" wrote:
"Jules" wrote in message

news






Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

No earth at the switch resulting in no short circuit to earth on the LT side
to stop engine- Hide quoted text -


LT side? i thought these things had no LT side and worked by having
the magnet whizz past the coil and generate the HT directly from
that. My old B+S had a strip of bendy metal bolted to the housing
next to the plug which you pressed onto the top contact of the plug
when you wnated it to stop.

Robert

On 14 May, 09:40, RobertL wrote:
On May 14, 6:20*am, "R" wrote:



"Jules" wrote in message

news

Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

No earth at the switch resulting in no short circuit to earth on the LT side
to stop engine- Hide quoted text -

LT side? * i thought these things had no LT side and worked by having
the magnet whizz past the coil and generate the HT directly from
that. * My old B+S had a strip of bendy metal bolted to the housing
next to the plug which you pressed onto the top contact of the plug
when you wnated it to stop.

Robert

I'm not sure how you switch off a magneto system with a key, but it
certainly sounds as if one of the wires from the insulated post is no
longer doing it's thing.

My 40 year B &S has the bent strip on the cylinder head as mentioned
above.

Rob

On Thu, 14 May 2009 09:31:27 +0100, AlanD wrote:
No earth at the switch resulting in no short circuit to earth on the LT
side to stop engine


He's tried shorting to ground already however.
I'd say the other end of the wire (magneto end) has become disconnected, or
that there is an internal break in it.

Yes, that occurred to me after I posted (it had been a long day!) - I'll
plonk the meter on it later and check that out. The odd thing though is
that the wire running down from the keyswitch to the post on the engine
seems to be bad too (either the wire or keyswitch, or switch ground as
someone mentioned) - but then this mower does seem to be posessed and
loves throwing multiple faults at me, so I wouldn't put it past it ;-)

cheers

J.

On Thu, 14 May 2009 10:23:21 -0500, Jules wrote:
Yes, that occurred to me after I posted (it had been a long day!) - I'll
plonk the meter on it later and check that out. The odd thing though is
that the wire running down from the keyswitch to the post on the engine
seems to be bad too (either the wire or keyswitch, or switch ground as
someone mentioned) - but then this mower does seem to be posessed and
loves throwing multiple faults at me, so I wouldn't put it past it ;-)

And the result was... multiple faults. Bad (intermittant) ground between
the chassis and the metal cowl which supports the instruments / switch /
steering wheel, *and* a break (intermittant) in the wire running from the
magneto to the side of the engine.

cheers

Jules

Jules wrote:
On Thu, 14 May 2009 10:23:21 -0500, Jules wrote:
Yes, that occurred to me after I posted (it had been a long day!) - I'll
plonk the meter on it later and check that out. The odd thing though is
that the wire running down from the keyswitch to the post on the engine
seems to be bad too (either the wire or keyswitch, or switch ground as
someone mentioned) - but then this mower does seem to be posessed and
loves throwing multiple faults at me, so I wouldn't put it past it ;-)

And the result was... multiple faults. Bad (intermittant) ground between
the chassis and the metal cowl which supports the instruments / switch /
steering wheel, *and* a break (intermittant) in the wire running from the
magneto to the side of the engine.

Ah, yes, a wire is not the same as a connection. Plastic insulation can hide a multitude of sins.

Fredxx wrote:
"Jules" wrote in message
news

Grrr. I got the B+S engine in the mower running (10HP sidevalve with
key start) - and then found that when I turn the key to shut it off, the
engine happily carries on; the only way to stop it was to pull the lead
for the spark plug off.

This particular engine has a magneto mounted beside the flywheel for spark
generation. There's a thin black wire which runs down from it to an
insulated post on the side of the engine, and from there a wire which goes
up to one of the terminals on the back of the keyswitch.

The wire seems to serve no useful purpose, which is presumably my problem
;-) Regardless of ignition switch position it does nothing - neither
showing a voltage nor connecting to chassis ground.

I tried shorting it to ground when the engine was running, but that
didn't work. Maybe it's supposed to give +12V with the ignition *off*?
(I'm reluctant to try that just on the offchance)

Any ideas?


If there's a bolt close to the plug, I'd be tempted to cut a strip of metal
which is shaped and of sufficient length to short out the plug when pushed
onto it, as seen in many old lawn mowers.

very effective way to teach kids to pay attention


NT

On Sat, 23 May 2009 17:52:36 +1200, Gib Bogle wrote:
And the result was... multiple faults. Bad (intermittant) ground between
the chassis and the metal cowl which supports the instruments / switch /
steering wheel, *and* a break (intermittant) in the wire running from the
magneto to the side of the engine.

Ah, yes, a wire is not the same as a connection. Plastic insulation
can hide a multitude of sins.

Indeed. The insulation around the wire looked good, but there was a break
just downstream of the connector on the side of the engine.

Two days ago I made a new bracket for part of the mower deck as the
original had buckled (resulting in blade slip under heavy load). Then
yesterday I made a new throttle cable and put on a new silencer (along
with some homebrew metalwork to secure it much better than the original
design). It now cuts beautifully and isn't deafening! :-)

cheers

Jules