The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Thanks,
Bob

"Bob Engelhardt" wrote in message ...

The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Thanks,
Bob

================================================== ========

[reply]

If you're going to take it to a repairman anyway, ask if he thinks it can be
reamed, rather than replaced. If so, have it done, and then lap it again.

It's hard to tell how deep those pits are, from the photo, but it's worth
asking.

--
Ed Huntress

Bob Engelhardt wrote:
The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Thanks,
Bob

That seat needs to be cut and probably you need a new valve as well.
I would take it in, have the seats done and new guides as well as new
valves.
Plus I'd have them check the bore and probably have it bored to the
first oversize possible.

Look at it this way, if you do it right it will last at least as long as
it did the first time. I have a few small engines around here
that are 50 years old+. As they turn from nice running engines into
mosquito foggers they get rebuilt back to factory spec.

Like I told one guy who brought in an old iron Kohler, As long as the
block is not broken in half the rest is reparable.
You can usually find a good crank (and some interchange up to current
numbers). Bore worn and they tell you that the pistons are no longer
available? Bore it out and sleeve it back to stock or to a common size.

--
Steve W.

On 11/21/2011 5:41 PM, Bob Engelhardt wrote:
The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Thanks,
Bob


Does the seat still have carbon on it or is it shiny? I don't see much
color difference in that picture, so can't be sure.

I would check that there is approx .010" lash to be sure the valve can
seat fully during lapping.

MikeB

--
Email is valid but not checked often

The one time I worked on a 5 HP briggs, it was a log
splitter that was way under powered. I cleaned the valves
with a wire brush, and it ran fine. I'd borrowed the
splitter, and he was pleased to get it back with an oil
change and better power.

Yours looks a bit worse than the one I remember. Well, a lot
worse. I remember that valve seat cutters from Belsaw were a
bit expensive. I don't remember off hand, how to get the
seat out, and replace. Heat, drive it with a pin punch,
probably.

Just for giggles, if that was my machine I'd wire brush the
seats and valves. Check valve clearance, put it back
together with new gasoline, and see how it runs. But, that's
me. I'm sure others will advise you to "do the right thing"
and have a good shop do it up. If you have the valve job,
set of gaskets, oil change, and so on. Then, you should have
years of service left.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Bob Engelhardt" wrote in
message ...
The engine on my leaf vac wouldn't start & I diagnosed low
compression.
It's a 5HP B&S. Here's a picture of the exhaust valve
seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair
Manual says that
after replacing a seat, it needs to be cut. How important
is the
cutting? I'm not about to buy a cutter & I'll take the
engine to a
repairman instead.

Thanks,
Bob

On Mon, 21 Nov 2011 17:41:59 -0500, Bob Engelhardt
wrote:

The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Thanks,
Bob

If you cut the valve seat or even just lap it in you reduce the valve
clearance. The end of the valve stem then needs to be ground off,
(flat and square), to get the proper valve lash. I don't remember the
spec.

The farther down you cut the valve seat the lower the compression
goes. Same goes for cutting the valve.

When you put it away for winter, a quick squirt of WD-40 in the carb
or spark plug hole is a good thing. Then slowly pull the starter rope
until you feel compression. Put it away like this, both valves are
closed and the combustuion chamber is sealed from moisture and rust.

Like the other poster said a wire brush and quick lap job shopuld get
you going for now.

Remove 333 to reply.
Randy

Bob Engelhardt wrote:
The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Well, I adjusted the valves, put it back together and tried it. The
compression was much better, but it still didn't start. It fact, it had
a terrible kick-back. Which was due to the flywheel key being sheared
and the timing being off by 90 degrees! Which was very likely the only
problem all along, even though the compression did test poorly.

The key replaced, it still doesn't start! Arrrgh! It has spark & won't
start even with gas squirted in the cylinder.

Well, maybe it's the valve clearances - that's the only thing that's
changed, right? They're close: the exhaust should be .009 - .011 & it's
11 (12 is nogo). The intake should be .005 - .007 & it's 8+ (9 is
tight). Is the clearance that important? Or is it likely something
else entirely? Although I don't know what that could be.

Befuddled,
Bob

Bob Engelhardt wrote:



The key replaced, it still doesn't start! Arrrgh! It has spark & won't
start even with gas squirted in the cylinder.

Well, maybe it's the valve clearances - that's the only thing that's
changed, right? They're close: the exhaust should be .009 - .011 & it's
11 (12 is nogo). The intake should be .005 - .007 & it's 8+ (9 is
tight). Is the clearance that important? Or is it likely something
else entirely? Although I don't know what that could be.
No, these small differences in valve clearance will not prevent it
from running. And, you say it does have compression. Well, there's
spark, and then there's SPARK. Maybe the spark is weak, due to a bad
coil, or a bad plug. Or, the spark timing could STILL be off. Do you
have a timing light? Does this have electronic (breakerless) ignition,
or is there a set of points buried under a cover under the flywheel?

Hmmmm, funny it had the kickback when the flywheel was out of time.
That indicates the spark was adequate then. That sort of indicates
spark blowout under compression, ie. a weak spark.

Jon

"Bob Engelhardt" wrote in message
...
Bob Engelhardt wrote:
The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Well, I adjusted the valves, put it back together and tried it. The
compression was much better, but it still didn't start. It fact, it had a
terrible kick-back. Which was due to the flywheel key being sheared and
the timing being off by 90 degrees! Which was very likely the only
problem all along, even though the compression did test poorly.

The key replaced, it still doesn't start! Arrrgh! It has spark & won't
start even with gas squirted in the cylinder.

Well, maybe it's the valve clearances - that's the only thing that's
changed, right? They're close: the exhaust should be .009 - .011 & it's
11 (12 is nogo). The intake should be .005 - .007 & it's 8+ (9 is tight).
Is the clearance that important? Or is it likely something else entirely?
Although I don't know what that could be.

Befuddled,
Bob

Change the spark plug.

The key replaced, it still doesn't start! Arrrgh! It has spark &
won't start even with gas squirted in the cylinder.

The sheared key is a common B&S problem when the ignition timing is off.

Have you checked the points gap?

Also, you said "it has spark". Is that _at_the_plug_, or just from the
wire to the block? (hint-- wet plugs often won't spark).

Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.

If they're too open, they'll be advanced. That can be caused by mis-
adjustment, but also by wear (burning).

LLoyd

"bw" fired this volley in
:

The key replaced, it still doesn't start! Arrrgh! It has spark &
won't start even with gas squirted in the cylinder.

Oh... BTW... don't squirt gas in the cylinder. First, it may wet the plug.
Second, it washes any oil off the cylinder walls, and can promote wear and
scoring.

Squirt a _little_ down the carb throat (maybe just 1/2cc). If if doesn't
"pop" then, you have a different problem.

LLoyd

On Wed, 21 Dec 2011 14:53:05 -0500, Bob Engelhardt
wrote:

Bob Engelhardt wrote:
The engine on my leaf vac wouldn't start & I diagnosed low compression.
It's a 5HP B&S. Here's a picture of the exhaust valve seat (after
lapping):
http://home.comcast.net/~bobengelhardt/ValveSeat.jpg

Does it (the seat) need to be replaced? The B&S Repair Manual says that
after replacing a seat, it needs to be cut. How important is the
cutting? I'm not about to buy a cutter & I'll take the engine to a
repairman instead.

Well, I adjusted the valves, put it back together and tried it. The
compression was much better, but it still didn't start. It fact, it had
a terrible kick-back. Which was due to the flywheel key being sheared
and the timing being off by 90 degrees! Which was very likely the only
problem all along, even though the compression did test poorly.

The key replaced, it still doesn't start! Arrrgh! It has spark & won't
start even with gas squirted in the cylinder.

Well, maybe it's the valve clearances - that's the only thing that's
changed, right? They're close: the exhaust should be .009 - .011 & it's
11 (12 is nogo). The intake should be .005 - .007 & it's 8+ (9 is
tight). Is the clearance that important? Or is it likely something
else entirely? Although I don't know what that could be.

Befuddled,
Bob
Have you tried a new spark plug, by chance??? They can look good and
STILL cause difficult starting.

If it's the Briggs I've worked on, the valve clearance can be LOT more
than that, and still run. The clearance is just so that when the engine
warms up, the valves get longer, and they might not close completely.

Try a dry spark plug. Gas in the cylinder probably flooded it all to hell. I
missed a lot of this thread. Did you just pull the cylinder head, or did you
have the crank shaft and cam shaft out?

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"Bob Engelhardt" wrote in message
...

Well, I adjusted the valves, put it back together and tried it. The
compression was much better, but it still didn't start. It fact, it had
a terrible kick-back. Which was due to the flywheel key being sheared
and the timing being off by 90 degrees! Which was very likely the only
problem all along, even though the compression did test poorly.

The key replaced, it still doesn't start! Arrrgh! It has spark & won't
start even with gas squirted in the cylinder.

Well, maybe it's the valve clearances - that's the only thing that's
changed, right? They're close: the exhaust should be .009 - .011 & it's
11 (12 is nogo). The intake should be .005 - .007 & it's 8+ (9 is
tight). Is the clearance that important? Or is it likely something
else entirely? Although I don't know what that could be.

Befuddled,
Bob

Been five years or so, since I worked on one of these. Thanks for the
reminder. Hey, Bob, got to make sure the ignition coil is very close to the
fly wheel. I like to rip a spark plug box apart. Put that between the
flywheel and the coil. Loosen the two 5/16 bolts from top of the coil, and
slide the coil in snug to the flywheel magnets. Tighten the hold down bolts.
Crank the fly wheel to get the cardboard out. I think the spec is .014 inch
air gap, but a spark plug box thickness works OK, too.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"Jon Elson" wrote in message
news No, these small differences in valve clearance will not prevent it
from running. And, you say it does have compression. Well, there's
spark, and then there's SPARK. Maybe the spark is weak, due to a bad
coil, or a bad plug. Or, the spark timing could STILL be off. Do you
have a timing light? Does this have electronic (breakerless) ignition,
or is there a set of points buried under a cover under the flywheel?

Hmmmm, funny it had the kickback when the flywheel was out of time.
That indicates the spark was adequate then. That sort of indicates
spark blowout under compression, ie. a weak spark.

Jon

It's probably wet, and needs a new nappy.

Check the air gap between igniton coil and fly wheel magnets. Should be .014
if memory serves.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"bw" wrote in message
...


Change the spark plug.

"Stormin Mormon" wrote in message
...
Been five years or so, since I worked on one of these. Thanks for the
reminder. Hey, Bob, got to make sure the ignition coil is very close to
the
fly wheel. I like to rip a spark plug box apart. Put that between the
flywheel and the coil. Loosen the two 5/16 bolts from top of the coil, and
slide the coil in snug to the flywheel magnets. Tighten the hold down
bolts.
Crank the fly wheel to get the cardboard out. I think the spec is .014
inch
air gap, but a spark plug box thickness works OK, too.


Later Briggs books spec the gap at .008 but I've seen sources say anything
from .002 to .014 is ok.

Another cheap source for a shim is aluminum cut from the side of a soda can.

Remember to check for bearing wear. Bearing wear allows the flywheel to
"wobble" enough to affect the magnet gap. After adjusting, rotate the
flywheel a couple times and check the magnet gap to make sure it doesn't rub
the coil.

I finally got back to this engine (life kept intruding).

Jon Elson wrote:
No, these small differences in valve clearance will not prevent it
from running.

Great, I didn't want to fool around with them any more.

... Does this have electronic (breaker less) ignition,
or is there a set of points buried under a cover under the flywheel?

It had points, then was converted to breaker less. The points are still
there & the wires cut.

Hmmmm, funny it had the kickback when the flywheel was out of time.
That indicates the spark was adequate then. ...

Maybe "kickback" wasn't the right term. 'Cause there wasn't ignition, I
think. What happened was, as I was pulling the start cord, there was a
very abrupt & solid stop. So much so that I hurt my rotator cuff, not
seriously, though.

I just occurred to me that maybe that was what sheared the flywheel key.
In fact, I just looked and it's sheared again! WTF?

Lloyd E. Sponenburgh wrote:
....
Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.
....

That's a new one for me. It does have the old points there, even though
they aren't used. Is it the plunger that does it? It fits, though,
'cause the key has sheared again.

Thanks,
Bob

Stormin Mormon wrote:
... Hey, Bob, got to make sure the ignition coil is very close to the
fly wheel. I like to rip a spark plug box apart. Put that between the
flywheel and the coil. ...

Yeah, I adjusted it the the Manual spec, forget what it was. Used a
feeler guage.

Bob

Lloyd E. Sponenburgh wrote:
Oh... BTW... don't squirt gas in the cylinder. First, it may wet the plug.
Second, it washes any oil off the cylinder walls, and can promote wear and
scoring.
....

I've been doing it for years. I don't believe the effects are
significant. Thanks, Bob

On Dec 23, 1:51*pm, Bob Engelhardt wrote:
I finally got back to this engine (life kept intruding).

Jon Elson wrote:

* No, these small differences in valve clearance will not prevent it
* from running.

Great, I didn't want to fool around with them any more.

* ... *Does this have electronic (breaker less) ignition,
* or is there a set of points buried under a cover under the flywheel?

It had points, then was converted to breaker less. *The points are still
there & the wires cut.

* Hmmmm, funny it had the kickback when the flywheel was out of time.
* That indicates the spark was adequate then. *...

Maybe "kickback" wasn't the right term. *'Cause there wasn't ignition, I
think. *What happened was, as I was pulling the start cord, there was a
very abrupt & solid stop. *So much so that I hurt my rotator cuff, not
seriously, though.

I just occurred to me that maybe that was what sheared the flywheel key.
* In fact, I just looked and it's sheared again! *WTF?

Lloyd E. Sponenburgh wrote:

...
* Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.
...

That's a new one for me. *It does have the old points there, even though
they aren't used. *Is it the plunger that does it? *It fits, though,
'cause the key has sheared again.

Thanks,
Bob

Authentic (though spark induced) pre-ignition.

World needs a handle that attaches to the pull-start handle that pops
loose beyond a certain tension.

Dave

Stormin Mormon wrote:
If it's the Briggs I've worked on, the valve clearance can be LOT more
than that, and still run. The clearance is just so that when the engine
warms up, the valves get longer, and they might not close completely.

Good.

Try a dry spark plug. Gas in the cylinder probably flooded it all to hell.

Did that.

I missed a lot of this thread. Did you just pull the cylinder head, or did you
have the crank shaft and cam shaft out?

Way back I had the crankcase open & thought that I had mis-timed the
valves. But I checked that & it's OK.

Thanks,
Bob

bw wrote:
Change the spark plug.

wrote:

Have you tried a new spark plug, by chance??? They can look good and
STILL cause difficult starting.

Yes - no change.

Thanks,
Bob

On Fri, 23 Dec 2011 11:10:13 -0800 (PST), Dave__67
wrote:

On Dec 23, 1:51*pm, Bob Engelhardt wrote:
I finally got back to this engine (life kept intruding).

Jon Elson wrote:

* No, these small differences in valve clearance will not prevent it
* from running.

Great, I didn't want to fool around with them any more.

* ... *Does this have electronic (breaker less) ignition,
* or is there a set of points buried under a cover under the flywheel?

It had points, then was converted to breaker less. *The points are still
there & the wires cut.

* Hmmmm, funny it had the kickback when the flywheel was out of time.
* That indicates the spark was adequate then. *...

Maybe "kickback" wasn't the right term. *'Cause there wasn't ignition, I
think. *What happened was, as I was pulling the start cord, there was a
very abrupt & solid stop. *So much so that I hurt my rotator cuff, not
seriously, though.

I just occurred to me that maybe that was what sheared the flywheel key.
* In fact, I just looked and it's sheared again! *WTF?

Lloyd E. Sponenburgh wrote:

...
* Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.
...

That's a new one for me. *It does have the old points there, even though
they aren't used. *Is it the plunger that does it? *It fits, though,
'cause the key has sheared again.

Thanks,
Bob

Authentic (though spark induced) pre-ignition.

World needs a handle that attaches to the pull-start handle that pops
loose beyond a certain tension.

Dave

With tendonitis in both shoulders, I can suggest a natural solution
that's very effective at doing that.

And it even comes with a siren. It sounds like "OUCH!!!", followed by
"goddamit."

I wouldn't mind so much except that the same siren goes off when I try
to surf cast with a heavy weight on the line.

--
Ed Huntress

bw wrote:
....
Remember to check for bearing wear. Bearing wear allows the flywheel to
"wobble" enough to affect the magnet gap. After adjusting, rotate the
flywheel a couple times and check the magnet gap to make sure it doesn't rub
the coil.

Just checked - it's OK.

Thanks,
Bob

Dave__67 wrote:
....
World needs a handle that attaches to the pull-start handle that pops
loose beyond a certain tension.

Yes! A cord version of a shear pin.

Bob

"Bob Engelhardt" wrote in message
...
I finally got back to this engine (life kept intruding).

Jon Elson wrote:
No, these small differences in valve clearance will not prevent it
from running.

Great, I didn't want to fool around with them any more.

... Does this have electronic (breaker less) ignition,
or is there a set of points buried under a cover under the flywheel?

It had points, then was converted to breaker less. The points are still
there & the wires cut.

Hmmmm, funny it had the kickback when the flywheel was out of time.
That indicates the spark was adequate then. ...

Maybe "kickback" wasn't the right term. 'Cause there wasn't ignition, I
think. What happened was, as I was pulling the start cord, there was a
very abrupt & solid stop. So much so that I hurt my rotator cuff, not
seriously, though.

I just occurred to me that maybe that was what sheared the flywheel key.
In fact, I just looked and it's sheared again! WTF?

Lloyd E. Sponenburgh wrote:
...
Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.
...

That's a new one for me. It does have the old points there, even though
they aren't used. Is it the plunger that does it? It fits, though,
'cause the key has sheared again.

Thanks,
Bob

Older engines were "Easy spins", which held the intake valve slightly open
for a small portion of the compression stroke, so the usual methods of
checking compression won't give accurate readings (and Briggs did not
publish figures). For those engines, Briggs recommended rotating the
flywheel in the opposite direction and looking for a sharp rebound.

Do you have the crank connected to the load? I'm wondering if the flywheel
needs the added inertia of the blower (like a vertical shaft mower needs the
blade). You could also try heating the ignition coil in an oven for a while
to drive out any moisture.

Bob Engelhardt wrote:

I finally got back to this engine (life kept intruding).

Jon Elson wrote:
No, these small differences in valve clearance will not prevent it
from running.

Great, I didn't want to fool around with them any more.

... Does this have electronic (breaker less) ignition,
or is there a set of points buried under a cover under the flywheel?

It had points, then was converted to breaker less. The points are still
there & the wires cut.

Hmmmm, funny it had the kickback when the flywheel was out of time.
That indicates the spark was adequate then. ...

Maybe "kickback" wasn't the right term. 'Cause there wasn't ignition, I
think. What happened was, as I was pulling the start cord, there was a
very abrupt & solid stop. So much so that I hurt my rotator cuff, not
seriously, though.

I just occurred to me that maybe that was what sheared the flywheel key.
In fact, I just looked and it's sheared again! WTF?

Lloyd E. Sponenburgh wrote:
...
Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.
...

That's a new one for me. It does have the old points there, even though
they aren't used. Is it the plunger that does it? It fits, though,
'cause the key has sheared again.

What he was describing was the ignition timing being advanced so that it
causes kick-back and that is what would shear the key. But that was
describing a point based ignition. If the points are disconnected then it
has nothing to do with the points. On the breakerless system the flywheel
key alignment is all that determines timing.

Assuming the breakerless system used to work correctly, my guess is you
just need to get the nut good and tight so that it doesn't shear.

-jim




Thanks,
Bob

Dave__67 wrote:

Authentic (though spark induced) pre-ignition.

World needs a handle that attaches to the pull-start handle that pops
loose beyond a certain tension.

Dave


Already been done. I believe it was either Tecumseh or Clinton that had
them. The end of the cord had a ball instead of the common pull
handle.The handgrip itself had a socke that the ball snapped into. When
you pulled it hard and either reached the end of the rope or the engine
kicked back the ball would pop free of the grip. They went away quick
because most people would pull them off every time they tried to start
the engine, then complain about how they came off.
If you look through the small engines during the years there were a LOT
of ideas used to make them "easier" to deal with. Anyone remember the
spring winder units or the kick started ones.

Personally I like the true solution I have on most of my engines. Flip a
switch or turn a key....

--
Steve W.

Rick wrote:

Older engines were "Easy spins", which held the intake valve slightly
open for a small portion of the compression stroke, so the usual methods
of checking compression won't give accurate readings (and Briggs did not
publish figures). For those engines, Briggs recommended rotating the
flywheel in the opposite direction and looking for a sharp rebound.

Yeah, the backwards rotation is the way that I checked it.

Do you have the crank connected to the load? I'm wondering if the
flywheel needs the added inertia of the blower (like a vertical shaft
mower needs the blade). ...

Ohhhh ... yes! Never occurred to me, but you're right. I have a
vertical lawn mower engine used without the blade I occasionally get the
_same_ "kickback". I'm gonna' try it with a load.

Thank you,
Bob

jim wrote:

What he was describing was the ignition timing being advanced so that it
causes kick-back and that is what would shear the key. ...

OK, that makes sense. I was thinking that the points themselves caused
it & I was having a hard time seeing how that could be.

Thanks,
Bob

Bob Engelhardt wrote:

jim wrote:

What he was describing was the ignition timing being advanced so that it
causes kick-back and that is what would shear the key. ...

OK, that makes sense. I was thinking that the points themselves caused
it & I was having a hard time seeing how that could be.

Thanks,
Bob

If this thing is designed to have a large inertial mass attached on the
other end of the crank then that could be aggravating the kick back
also. But usually a horizontal 5hp would just have a small pulley to
drive a belt.

-jim

On Fri, 23 Dec 2011 15:56:55 -0500, Bob Engelhardt
wrote:

jim wrote:

What he was describing was the ignition timing being advanced so that it
causes kick-back and that is what would shear the key. ...

OK, that makes sense. I was thinking that the points themselves caused
it & I was having a hard time seeing how that could be.

Some of these small engines have a compression release on the exhaust
valve train to lower the compression enough to crank it. You have to
know the factory way to adjust the exhaust valve to allow for this or
the compression plus ignition kickback is nasty.
One Briggs, you have to find tdc piston on the fire stroke then turn
past tdc for a certain piston drop then set the exhaust valve
clearance there. Maybe some similar trick on your engine.
--
Mr.E

Bob Engelhardt wrote:
Rick wrote:
snip
Do you have the crank connected to the load? I'm wondering if the
flywheel needs the added inertia of the blower (like a vertical shaft
mower needs the blade). ...

Ohhhh ... yes! Never occurred to me, but you're right. I have a
vertical lawn mower engine used without the blade I occasionally get the
_same_ "kickback". I'm gonna' try it with a load.

This motor is used on a leaf vac. The load is a fan of 1/4" steel that
must weigh 6 - 8 lbs. I put the fan on, tried starting it, and it ran!
Pretty scary, though, with that fan running exposed!

I'm tempted to say "Problem solved", but it was loaded when this whole
problem started! So, I'm hopeful, but cautiously so.

Thanks again,
Bob

jim wrote:
If this thing is designed to have a large inertial mass attached on the
other end of the crank then that could be aggravating the kick back
also. But usually a horizontal 5hp would just have a small pulley to
drive a belt.

It drives a leaf vac. And has a longer shaft for the fan (I think). So
maybe the engine was designed for it and does need the mass. Maybe.

At any rate, it does run with the fan on, as reported. We'll see.

Bob

Mr.E wrote:
....
One Briggs, you have to find tdc piston on the fire stroke then turn
past tdc for a certain piston drop then set the exhaust valve
clearance there.

The Service Manual says to go past TDC by 1/4" drop. For all engines.
That's what I did.

Bob

On Dec 23, 4:13*pm, jim wrote:

If this thing is designed to have a large inertial mass attached on the
other end of the crank then that could be aggravating the kick back
also. But usually a horizontal 5hp would just have a small pulley to
drive a belt.

-jim

Horizontal engines usually have a substancial flywheel / blower. Some
vertical engines used on lawn mowers have a lighter flywheel and
depend on the blade to act as part of the flywheel.

Dan

On Fri, 23 Dec 2011 17:33:25 -0500, Bob Engelhardt
wrote:

jim wrote:
If this thing is designed to have a large inertial mass attached on the
other end of the crank then that could be aggravating the kick back
also. But usually a horizontal 5hp would just have a small pulley to
drive a belt.

It drives a leaf vac. And has a longer shaft for the fan (I think). So
maybe the engine was designed for it and does need the mass. Maybe.

At any rate, it does run with the fan on, as reported. We'll see.

Bob
Aluminum flywheel, or cast iron??
If it is an aluminum flywheel it will be virtually impossible to start
without the mass of a blade or other load connected.

On Fri, 23 Dec 2011 14:17:41 -0500, Ed Huntress
wrote:

On Fri, 23 Dec 2011 11:10:13 -0800 (PST), Dave__67
wrote:

On Dec 23, 1:51Â*pm, Bob Engelhardt wrote:
I finally got back to this engine (life kept intruding).

Jon Elson wrote:

Â* No, these small differences in valve clearance will not prevent it
Â* from running.

Great, I didn't want to fool around with them any more.

Â* ... Â*Does this have electronic (breaker less) ignition,
Â* or is there a set of points buried under a cover under the flywheel?

It had points, then was converted to breaker less. Â*The points are still
there & the wires cut.

Â* Hmmmm, funny it had the kickback when the flywheel was out of time.
Â* That indicates the spark was adequate then. Â*...

Maybe "kickback" wasn't the right term. Â*'Cause there wasn't ignition, I
think. Â*What happened was, as I was pulling the start cord, there was a
very abrupt & solid stop. Â*So much so that I hurt my rotator cuff, not
seriously, though.

I just occurred to me that maybe that was what sheared the flywheel key.
Â* In fact, I just looked and it's sheared again! Â*WTF?

Lloyd E. Sponenburgh wrote:

...
Â* Since (DAMHIKT) the points gap can shear a key, I'd be looking at that.
...

That's a new one for me. Â*It does have the old points there, even though
they aren't used. Â*Is it the plunger that does it? Â*It fits, though,
'cause the key has sheared again.

Thanks,
Bob

Authentic (though spark induced) pre-ignition.

World needs a handle that attaches to the pull-start handle that pops
loose beyond a certain tension.

Dave

With tendonitis in both shoulders, I can suggest a natural solution
that's very effective at doing that.

And it even comes with a siren. It sounds like "OUCH!!!", followed by
"goddamit."

I wouldn't mind so much except that the same siren goes off when I try
to surf cast with a heavy weight on the line.

Ed - if you have calcific tendonitis in your shoulders - which I also
suffer from, try magnesium suppliments. I take 600mg daily for the
last year and the improvement is remarkable. My left shoulder was not
as bad as my right and I had surgery on it (decompressive
acromioplasty and removal of bursa) on the left before discovering the
link to magnesium deficiency. I started on the magnesium, and within
months the right shoulder was as good as the repaired left, and within
6 months both had improved markedly.

If you take too much you'll just get the "runs" and you adjust your
dosage down accordingly.

On 11/22/2011 12:33 AM, Stormin Mormon wrote:
The one time I worked on a 5 HP briggs, it was a log
splitter that was way under powered. I cleaned the valves
with a wire brush, and it ran fine. I'd borrowed the
splitter, and he was pleased to get it back with an oil
change and better power.

Yours looks a bit worse than the one I remember. Well, a lot
worse. I remember that valve seat cutters from Belsaw were a
bit expensive. I don't remember off hand, how to get the
seat out, and replace. Heat, drive it with a pin punch,
probably.

Just for giggles, if that was my machine I'd wire brush the
seats and valves. Check valve clearance, put it back
together with new gasoline, and see how it runs. But, that's
me. I'm sure others will advise you to "do the right thing"
and have a good shop do it up. If you have the valve job,
set of gaskets, oil change, and so on. Then, you should have
years of service left.


A good wire brush will fix EVERYTHING!

wrote:
Aluminum flywheel, or cast iron??
If it is an aluminum flywheel it will be virtually impossible to start
without the mass of a blade or other load connected.

Cast iron