I have a rotary petrol mower, powered by a Briggs & Stratton HP470. Yesterday I hit a kerb stone and the engine stopped dead.

I retarted it and it sounded really rough and was vibrating. I removed the cutter blade and bent it back to level, sharpened and balanced it (as best I could).

Upon re-starting it sounds like a bag of spanners! No smoke but really noisy, rough and the engine speed is uneven.

Have I wrecked the crankshaft bearings or can ayone suggest what else it might be please?

"Geoff Griffiths" wrote in
message ...

I have a rotary petrol mower, powered by a Briggs & Stratton HP470.
Yesterday I hit a kerb stone and the engine stopped dead.

I retarted it and it sounded really rough and was vibrating. I removed
the cutter blade and bent it back to level, sharpened and balanced it
(as best I could).

Upon re-starting it sounds like a bag of spanners! No smoke but really
noisy, rough and the engine speed is uneven.

Have I wrecked the crankshaft bearings or can ayone suggest what else
it might be please?




--
Geoff Griffiths

The key holding the flywheel in position could be sheared, altering the
ignition timing. Or the flywheel could be damaged. Either case is the usual
result of an engine coming to an abrupt stop.

Geoff Griffiths wrote:
I have a rotary petrol mower, powered by a Briggs & Stratton HP470.
Yesterday I hit a kerb stone and the engine stopped dead.

I retarted it and it sounded really rough and was vibrating. I removed
the cutter blade and bent it back to level, sharpened and balanced it
(as best I could).

Upon re-starting it sounds like a bag of spanners! No smoke but really
noisy, rough and the engine speed is uneven.

Have I wrecked the crankshaft bearings or can ayone suggest what else
it might be please?




I have no idea what a bag of spanners sounds like but I'd bet you bent
the crankshaft. Take the spark plug out, keep your eye on the blade bolt
and pull the starter rope. If the bolt head appears to wobble then the
crankshaft is bent. Not much you can do about it. I've whacked them
pretty close to strait with a 5lb maul but you will likely never get rid
of the vibration.

--
Art

Chas Hurst wrote:
"Geoff Griffiths" wrote in
message ...
I have a rotary petrol mower, powered by a Briggs & Stratton HP470.
Yesterday I hit a kerb stone and the engine stopped dead.

I retarted it and it sounded really rough and was vibrating. I removed
the cutter blade and bent it back to level, sharpened and balanced it
(as best I could).

Upon re-starting it sounds like a bag of spanners! No smoke but really
noisy, rough and the engine speed is uneven.

Have I wrecked the crankshaft bearings or can ayone suggest what else
it might be please?




--
Geoff Griffiths

The key holding the flywheel in position could be sheared, altering the
ignition timing. Or the flywheel could be damaged. Either case is the usual
result of an engine coming to an abrupt stop.


A sheared key would cause it to not run.

--
Art

I think I'd take the blade off and match a new one at store and try
new IIRC at 3600 rpm it doesn't take much out of balance to rattle.
Also you might have partly sheared the flywheel key as mentioned.
There is a special tool about $2 USD you can buy or use nut hammer
screwdriver trick. Keys are about .25 or so.

Thanks for the replies folks.

"try new IIRC at 3600 rpm it doesn't take much out of balance to rattle"

can you please explain what the above means (IIRC)?

I have tried to watch the blade retaining nut whilst trying to pull the cord but it's really difficult. I also turned the blade by hand but couldn't detect any non-concentric movement.

Would running the mower without a blade attached show if it's the blade causing the problems?

I have noticed it makes quite a loud 'clunking-type rattle' just as the engine stops - any more thoughts please?

Geoff Griffiths wrote:
Thanks for the replies folks.

"try new IIRC at 3600 rpm it doesn't take much out of balance to
rattle"

can you please explain what the above means (IIRC)?

It stands for "If I recall Correctly" and the statement is nonsense.


I have tried to watch the blade retaining nut whilst trying to pull the
cord but it's really difficult. I also turned the blade by hand but
couldn't detect any non-concentric movement.

It's usually a bolt. At least here in the US. Not sure what the norm is
in the UK. Removing the spark plug so the engine will spin freely and
smoothly is a critical step. Otherwise it bounces around and is
impossible to see a wobble.


Would running the mower without a blade attached show if it's the blade
causing the problems?

Not a good idea. Most mowers use the blade as a flywheel and won't run
without the blade attached.


I have noticed it makes quite a loud 'clunking-type rattle' just as the
engine stops - any more thoughts please?




That clunking sound means the blade is loose. Remove it and the adapter
and examine for anything sheared or broken. Replace as needed and
tighten it up.

--
Art

"Art" wrote in message
...
Geoff Griffiths wrote:
Thanks for the replies folks.

"try new IIRC at 3600 rpm it doesn't take much out of balance to
rattle"

can you please explain what the above means (IIRC)?

It stands for "If I recall Correctly" and the statement is nonsense.


I have tried to watch the blade retaining nut whilst trying to pull the
cord but it's really difficult. I also turned the blade by hand but
couldn't detect any non-concentric movement.

It's usually a bolt. At least here in the US. Not sure what the norm is
in the UK. Removing the spark plug so the engine will spin freely and
smoothly is a critical step. Otherwise it bounces around and is
impossible to see a wobble.


Would running the mower without a blade attached show if it's the blade
causing the problems?

Not a good idea. Most mowers use the blade as a flywheel and won't run
without the blade attached.


I have noticed it makes quite a loud 'clunking-type rattle' just as the
engine stops - any more thoughts please?




That clunking sound means the blade is loose. Remove it and the adapter
and examine for anything sheared or broken. Replace as needed and
tighten it up.

--
Art

Some of the B&S engines have a bag of spanners inside, just under the debris
cover. Well, actually it's some little steel balls that act as a sort of
cintrifugal clutch in case you should hit a big root. Maybe your balls are
stuck. Simply cleaning them and perhaps a little spray lube such as WD-40
should get them working again. Like Art said, don't run it without the
blade. It's part of the whole.

I have an old (23 years) B&S 3.5 HP mower and I've hit concrete curbs and
other horrible stuff with it and it has never even sheared the flywheel key.
It always turned out to be the little steel balls (plus replacing mangled
blades). After removing the debris cover (assuming this model is the same
as mine) there will be a nut/bolt in the middle on the top. Remove that.
When you lift the shaft it will misalign the steel balls from the mechanism
and it can be a bit tricky to get them back in the right place. The are a
bit like washing machine agitator dogs.

Ulysses wrote:
"Art" wrote in message
...
Geoff Griffiths wrote:
Thanks for the replies folks.

"try new IIRC at 3600 rpm it doesn't take much out of balance to
rattle"

can you please explain what the above means (IIRC)?
It stands for "If I recall Correctly" and the statement is nonsense.

I have tried to watch the blade retaining nut whilst trying to pull the
cord but it's really difficult. I also turned the blade by hand but
couldn't detect any non-concentric movement.
It's usually a bolt. At least here in the US. Not sure what the norm is
in the UK. Removing the spark plug so the engine will spin freely and
smoothly is a critical step. Otherwise it bounces around and is
impossible to see a wobble.

Would running the mower without a blade attached show if it's the blade
causing the problems?
Not a good idea. Most mowers use the blade as a flywheel and won't run
without the blade attached.

I have noticed it makes quite a loud 'clunking-type rattle' just as the
engine stops - any more thoughts please?



That clunking sound means the blade is loose. Remove it and the adapter
and examine for anything sheared or broken. Replace as needed and
tighten it up.

--
Art

Some of the B&S engines have a bag of spanners inside, just under the debris
cover. Well, actually it's some little steel balls that act as a sort of
cintrifugal clutch in case you should hit a big root. Maybe your balls are
stuck. Simply cleaning them and perhaps a little spray lube such as WD-40
should get them working again. Like Art said, don't run it without the
blade. It's part of the whole.

I have an old (23 years) B&S 3.5 HP mower and I've hit concrete curbs and
other horrible stuff with it and it has never even sheared the flywheel key.
It always turned out to be the little steel balls (plus replacing mangled
blades). After removing the debris cover (assuming this model is the same
as mine) there will be a nut/bolt in the middle on the top. Remove that.
When you lift the shaft it will misalign the steel balls from the mechanism
and it can be a bit tricky to get them back in the right place. The are a
bit like washing machine agitator dogs.


You haven't a clue as to what you are talking about. Those little steel
balls are part of the starter clutch and have nothing whatsoever to do
with hitting anything. When the engine is not spinning they fall down
and to the center and allow the starter drive to push them and they in
turn push the flywheel nut. Once the engine begins spinning centrifugal
force pushes them to the out side. Then the starter can no longer engage.

--
Art

"Art" wrote in message
...
Ulysses wrote:
"Art" wrote in message
...
Geoff Griffiths wrote:
Thanks for the replies folks.

"try new IIRC at 3600 rpm it doesn't take much out of balance to
rattle"

can you please explain what the above means (IIRC)?
It stands for "If I recall Correctly" and the statement is nonsense.

I have tried to watch the blade retaining nut whilst trying to pull
the
cord but it's really difficult. I also turned the blade by hand but
couldn't detect any non-concentric movement.
It's usually a bolt. At least here in the US. Not sure what the norm is
in the UK. Removing the spark plug so the engine will spin freely and
smoothly is a critical step. Otherwise it bounces around and is
impossible to see a wobble.

Would running the mower without a blade attached show if it's the
blade
causing the problems?
Not a good idea. Most mowers use the blade as a flywheel and won't run
without the blade attached.

I have noticed it makes quite a loud 'clunking-type rattle' just as
the
engine stops - any more thoughts please?



That clunking sound means the blade is loose. Remove it and the adapter
and examine for anything sheared or broken. Replace as needed and
tighten it up.

--
Art

Some of the B&S engines have a bag of spanners inside, just under the
debris
cover. Well, actually it's some little steel balls that act as a sort
of
cintrifugal clutch in case you should hit a big root. Maybe your balls
are
stuck. Simply cleaning them and perhaps a little spray lube such as
WD-40
should get them working again. Like Art said, don't run it without the
blade. It's part of the whole.

I have an old (23 years) B&S 3.5 HP mower and I've hit concrete curbs
and
other horrible stuff with it and it has never even sheared the flywheel
key.
It always turned out to be the little steel balls (plus replacing
mangled
blades). After removing the debris cover (assuming this model is the
same
as mine) there will be a nut/bolt in the middle on the top. Remove
that.
When you lift the shaft it will misalign the steel balls from the
mechanism
and it can be a bit tricky to get them back in the right place. The are
a
bit like washing machine agitator dogs.


You haven't a clue as to what you are talking about. Those little steel
balls are part of the starter clutch and have nothing whatsoever to do
with hitting anything. When the engine is not spinning they fall down
and to the center and allow the starter drive to push them and they in
turn push the flywheel nut. Once the engine begins spinning centrifugal
force pushes them to the out side. Then the starter can no longer engage.

--
Art

That might explain why my lawn is sudsy and my clothes get all chopped up in
the washer.