I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never really
performed well, its key issue being that the (fixed) throttle has always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service this
winter and had a look at the manual to see if I could get a feel for the
throttle setting, so I can tickle it up a bit. The manual is very clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be that
they think any punter is likely to render it FUBAR and never rediscover
the right setting range, or perhaps that it would simply use a bit more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

On 10/16/2016 1:32 PM, GMM wrote:
I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never really
performed well, its key issue being that the (fixed) throttle has always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service this
winter and had a look at the manual to see if I could get a feel for the
throttle setting, so I can tickle it up a bit. The manual is very clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be that
they think any punter is likely to render it FUBAR and never rediscover
the right setting range, or perhaps that it would simply use a bit more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.

On 16/10/2016 13:46, newshound wrote:
On 10/16/2016 1:32 PM, GMM wrote:
I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never really
performed well, its key issue being that the (fixed) throttle has always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service this
winter and had a look at the manual to see if I could get a feel for the
throttle setting, so I can tickle it up a bit. The manual is very clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be that
they think any punter is likely to render it FUBAR and never rediscover
the right setting range, or perhaps that it would simply use a bit more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

On Sunday, 16 October 2016 16:27:20 UTC+1, GMM wrote:
On 16/10/2016 13:46, newshound wrote:
On 10/16/2016 1:32 PM, GMM wrote:
I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never really
performed well, its key issue being that the (fixed) throttle has always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service this
winter and had a look at the manual to see if I could get a feel for the
throttle setting, so I can tickle it up a bit. The manual is very clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be that
they think any punter is likely to render it FUBAR and never rediscover
the right setting range, or perhaps that it would simply use a bit more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

The governor is usually a flap in a cooling air stream.
Hunting is usually caused by stiction in this linkage somewhere.

On 16/10/2016 17:20, harry wrote:
On Sunday, 16 October 2016 16:27:20 UTC+1, GMM wrote:
On 16/10/2016 13:46, newshound wrote:
On 10/16/2016 1:32 PM, GMM wrote:
I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never really
performed well, its key issue being that the (fixed) throttle has always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service this
winter and had a look at the manual to see if I could get a feel for the
throttle setting, so I can tickle it up a bit. The manual is very clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be that
they think any punter is likely to render it FUBAR and never rediscover
the right setting range, or perhaps that it would simply use a bit more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

The governor is usually a flap in a cooling air stream.

Agreed,

Hunting is usually caused by stiction in this linkage somewhere.

It can also be indicative of a wrongly set mixture.

On 16/10/2016 16:27, GMM wrote:
On 16/10/2016 13:46, newshound wrote:
On 10/16/2016 1:32 PM, GMM wrote:
I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never really
performed well, its key issue being that the (fixed) throttle has always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service this
winter and had a look at the manual to see if I could get a feel for the
throttle setting, so I can tickle it up a bit. The manual is very clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be that
they think any punter is likely to render it FUBAR and never rediscover
the right setting range, or perhaps that it would simply use a bit more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

If you do dismantle it, make a note of spring positions and which holes
in the throttle and air flap assemblies are being used by the spring
and/or other linkage.

In message , Fredxxx
writes

If you do dismantle it, make a note of spring positions and which holes
in the throttle and air flap assemblies are being used by the spring
and/or other linkage.

In these digital days, I try to remember to take lots of photos as I
dismantle stuff. Makes putting it all back together somewhat easier.
--
Graeme

On 16/10/2016 16:27, GMM wrote:
On 16/10/2016 13:46, newshound wrote:

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

The governors on most lawnmower engines are pretty crude. When the
engine isn't running, a spring holds the throttle fully open. When the
engine starts and gathers speed, a vane inside the engine cowl - which
is connected to the throttle - is blown by the draft from the engine
cooling fan in a direction which tends to close the throttle. So - in
theory - you end up with a sort of dynamic equilibrium, with the
throttle open just wide enough to maintain speed. If the load increases
- as, for example, when the blade encounters a clump of grass - the
engine slows a bit, the vane gets blown a bit less enabling the throttle
to open a bit more.

That's how it's *supposed* to work, but it's all a bit delicate, with a
system of springs and levers which must all be able to move freely as
required. A common fault is for grass cuttings to find their way inside
the engine cowl such that they interfere with the operation of the vane.
It would be worth removing the cowl and cleaning out any debris, and
making sure that all parts of the throttle mechanism can move freely.

Is it Mountfield's own engine. I've got a Mountfield mower with a Briggs
and Stratton Engine, which I bought at a car boot sale, and it came
without any documentation. B&S were very helpful in sending me some
information about how to set it all up, and it's now working fine.

I bought a cheap stroboscope (optical tachometer) on Ebay to enable me
to measure the no-load speed. You may care to do the same if you can't
find anything obviously wrong with your engine, but it just doesn't run
fast enough. There almost certainly *is* some adjustment but, if it's
like B&S, it involves bending bits of metal rather than turning an
adjustment screw - which is probably why they tell you not to do it!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

Or the person lives on the top of a mountain...:-)
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Fredxxx" wrote in message
...
On 16/10/2016 17:20, harry wrote:
On Sunday, 16 October 2016 16:27:20 UTC+1, GMM wrote:
On 16/10/2016 13:46, newshound wrote:
On 10/16/2016 1:32 PM, GMM wrote:
I have a Mountfield (aka B&Q) HP454 with a V35 motor (though the spec
probably isn't important). Had it for 4 - 5 years and it's never
really
performed well, its key issue being that the (fixed) throttle has
always
felt too slow, so the engine tends to hunt.
It's hardly been pampered, but I thought I might give it a service
this
winter and had a look at the manual to see if I could get a feel for
the
throttle setting, so I can tickle it up a bit. The manual is very
clear
that the throttle shouldn't be touched, but doesn't say why.

Does anyone have any idea of the reasoning behind this? It may be
that
they think any punter is likely to render it FUBAR and never
rediscover
the right setting range, or perhaps that it would simply use a bit
more
fuel.

Obviously, a good service might be expected to improve things anyway,
but I doubt it, as it's always been like this.

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

The governor is usually a flap in a cooling air stream.

Agreed,

Hunting is usually caused by stiction in this linkage somewhere.

It can also be indicative of a wrongly set mixture.

On 16/10/2016 19:55, Roger Mills wrote:
On 16/10/2016 16:27, GMM wrote:
On 16/10/2016 13:46, newshound wrote:

I guess then that this is a machine with a governor that maintains revs
by increasing fuel when the load increases. I have this on a powered
wheelbarrow and a water pump.
Well I guess that's the principle, although it has never seemed to
respond to any increased load by anything other than slowing down and/or
stalling. Certainly it seems to have a sprung governor.

The governors on most lawnmower engines are pretty crude. When the
engine isn't running, a spring holds the throttle fully open. When the
engine starts and gathers speed, a vane inside the engine cowl - which
is connected to the throttle - is blown by the draft from the engine
cooling fan in a direction which tends to close the throttle. So - in
theory - you end up with a sort of dynamic equilibrium, with the
throttle open just wide enough to maintain speed. If the load increases
- as, for example, when the blade encounters a clump of grass - the
engine slows a bit, the vane gets blown a bit less enabling the throttle
to open a bit more.

That's how it's *supposed* to work, but it's all a bit delicate, with a
system of springs and levers which must all be able to move freely as
required. A common fault is for grass cuttings to find their way inside
the engine cowl such that they interfere with the operation of the vane.
It would be worth removing the cowl and cleaning out any debris, and
making sure that all parts of the throttle mechanism can move freely.

Is it Mountfield's own engine. I've got a Mountfield mower with a Briggs
and Stratton Engine, which I bought at a car boot sale, and it came
without any documentation. B&S were very helpful in sending me some
information about how to set it all up, and it's now working fine.

I bought a cheap stroboscope (optical tachometer) on Ebay to enable me
to measure the no-load speed. You may care to do the same if you can't
find anything obviously wrong with your engine, but it just doesn't run
fast enough. There almost certainly *is* some adjustment but, if it's
like B&S, it involves bending bits of metal rather than turning an
adjustment screw - which is probably why they tell you not to do it!

My Hayter has a B&S motor, and I always found this ran a bit too slow,
and as a result the airflow though the grass collection path was too low
and it kept clogging. Judicious application of a short length of copper
wire around the spring assembly allowed the spring to be "tightened"
just a tad, and that does the trick. The copper wire is easier to bend
around than the metalwork of the machine.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Sun, 16 Oct 2016 19:55:01 +0100, Roger Mills
wrote:

snip

That's how it's *supposed* to work, but it's all a bit delicate, with a
system of springs and levers which must all be able to move freely as
required. A common fault is for grass cuttings to find their way inside
the engine cowl such that they interfere with the operation of the vane.
It would be worth removing the cowl and cleaning out any debris, and
making sure that all parts of the throttle mechanism can move freely.

snip A complete aside but my mate in the garage was asked to replace
a 'noisy' cabin heater fan on an Audi (I think it was) and was
provided a replacement s/h (tangential) fan unit to do it with. When
he got the old fan unit out and much to his surprise he found a bundle
of cable sitting in the fan itself!

It looked like it was a thin coax of some sort, possibly a GPS aerial
extension lead but I'm not sure how it could have got in there?

Cheers, T i m

Thanks all.

It seems the answer is simply that the avergae person will make a mess
if they try to fiddle with it then, rather than it causing a problem per se.
The thought of having to bend things to make adjustments seems a bit
crude, but hopefully it's not impossible to get some more performance
out of this. Must have a look for the copper wire!

Cheers

GMM posted
Thanks all.

It seems the answer is simply that the avergae person will make a mess
if they try to fiddle with it then, rather than it causing a problem
per se.
The thought of having to bend things to make adjustments seems a bit
crude, but hopefully it's not impossible to get some more performance
out of this. Must have a look for the copper wire!

A well-known fault on some types of Toro lawnmower (which are based on
earlier Hayter models, I think) happens when the front of the mower
collides with a solid object such as a tree trunk. When this happens,
the metal brace that anchors one end of the governor spring can be bent
inwards, slackening the spring and causing the engine to run below full
power. The solution is simply to bend the brace back out again.

--
Jack