Correct speed for rotary lawnmower engine?
 

I've got a 21" Toro self propelled rotary mower with a 3.75 hp Briggs
engine on it.

Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it.

I measured the RPMs with my non-contact tach and the engines's "full
speed" with no load was 3,000 RPMs, and it didn't sound like it dropped
off significantly under load.

My memory is telling me governed full speed for that kind of setup
should be more like 3,500 RPM. Can someone confirm that?

The governor seems to be doing it's job, but I've got a feeling it's
spring has stretched a bit over the years. The engine speed will
increase fine if I "assist" the spring with my fingertips, so I can
probably tweak the speed up by rebending the throttle lever end of the
spring to make it a bit shorter, (or by buying a new spring). The other
end of the spring is as far away from the throttle lever as the speed
control lever can go.

Thanks guys,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Correct speed for rotary lawnmower engine?
 

On May 9, 1:30?pm, Jeff Wisnia wrote:
I've got a 21" Toro self propelled rotary mower with a 3.75 hp Briggs
engine on it.

Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it.

I measured the RPMs with my non-contact tach and the engines's "full
speed" with no load was 3,000 RPMs, and it didn't sound like it dropped
off significantly under load.

My memory is telling me governed full speed for that kind of setup
should be more like 3,500 RPM. Can someone confirm that?

The governor seems to be doing it's job, but I've got a feeling it's
spring has stretched a bit over the years. The engine speed will
increase fine if I "assist" the spring with my fingertips, so I can
probably tweak the speed up by rebending the throttle lever end of the
spring to make it a bit shorter, (or by buying a new spring). The other
end of the spring is as far away from the throttle lever as the speed
control lever can go.

Thanks guys,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Perhaps this is a feature where the aging of the machine matches aging
of the operator? But apparently you're not ready for that yet... All
I know is these 1- speed engines are designed to run at their set
speed, they warn against tampering, so check the specs before any
sdjustments.

Correct speed for rotary lawnmower engine?
 

On May 9, 1:30 pm, Jeff W3
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Also of interest is speed/longevity. These engines are not pressure-
lubed at main/rod journals. So ... I'll wager that your longevity
at 3K rpm will be much greater than at 3.5K.

HTH,
J

Correct speed for rotary lawnmower engine?
 

"Jeff Wisnia" wrote in message
...

I've got a 21" Toro self propelled rotary mower with a 3.75 hp Briggs
engine on it.

Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it

Most newer mowers don't even have a throttle control - they run full-tilt
all the time. Mine does anyhow. They do this partly to save money but also
because the control just isn't needed.

Correct speed for rotary lawnmower engine?
 

3,600 is typical for these engines. They will tolerate more however. We
set most of ours to 4,000 - 4,100

--
Steve Barker




"Jeff Wisnia" wrote in message
...

I've got a 21" Toro self propelled rotary mower with a 3.75 hp Briggs
engine on it.

Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it.

I measured the RPMs with my non-contact tach and the engines's "full
speed" with no load was 3,000 RPMs, and it didn't sound like it dropped
off significantly under load.

My memory is telling me governed full speed for that kind of setup should
be more like 3,500 RPM. Can someone confirm that?

The governor seems to be doing it's job, but I've got a feeling it's
spring has stretched a bit over the years. The engine speed will increase
fine if I "assist" the spring with my fingertips, so I can probably tweak
the speed up by rebending the throttle lever end of the spring to make it
a bit shorter, (or by buying a new spring). The other end of the spring is
as far away from the throttle lever as the speed control lever can go.

Thanks guys,

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Correct speed for rotary lawnmower engine?
 

They don't run "full tilt". They are still governed at 3600 even without a
throttle control.

--
Steve Barker




"Bob M." wrote in message
. ..

"Jeff Wisnia" wrote in message
...

I've got a 21" Toro self propelled rotary mower with a 3.75 hp Briggs
engine on it.

Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it

Most newer mowers don't even have a throttle control - they run full-tilt
all the time. Mine does anyhow. They do this partly to save money but
also because the control just isn't needed.

Correct speed for rotary lawnmower engine?
 

"Jeff Wisnia" wrote in message
...

Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it.


Are you sure the self propelling drive is not slipping?

Correct speed for rotary lawnmower engine?
 

Edwin Pawlowski wrote:

"Jeff Wisnia" wrote in message
...


Whe I used it today for the first time this season I had a feeling the
engine might be running a little slower than it had in the past, as I
seemed to be walking "less fast" to keep up with it.



Are you sure the self propelling drive is not slipping?



I doubt that Ed, there's only one belt between the engine shaft and the
worm gear reduction box on the front axle.

That belt is tighter than a bull's arse in fly season.

My Toro mower is about 30 year old now. It's original Tecumsah engine
wore to the point where you could barely feel any compression when
pulling it over, so I replaced it about six years ago with the present
B&S which I ordered from Northern Tool.

I figger that if I'm faithfull to my tools and maintain them they'll
respond in kind, and from what I can see, my old Toro mower is built a
lot sturdier that the crap on sale now. Same goes for my Airen's
Sno-Thro, "The widow maker"* which just completed its 42nd winter
clearing our driveway.

Jeff

* So named by me because it's totally devoid of any of those "safety"
features Airen's has been blackmailed into adding to their machines by
legions of scumbag lawyers. (Just my .02)

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

Correct speed for rotary lawnmower engine?
 

Steve Barker wrote:

3,600 is typical for these engines. They will tolerate more however. We
set most of ours to 4,000 - 4,100


Thanks Steve. I'll tweak it up to 3600 this weekend.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.