Hi,

I hope this is the right group to post this question to - I couldnt
find a lawnmower specific group.

I have just purchased a Flymo XL500 petrol lawnmower. Upon starting it
for the first time yesterday, I noticed that for the first second or
two it makes a kind of knocking noise - as if the blade was slightly
loose or something. It also makes the same noise when stopping. While
running normally, cutting the grass, the noise is not there at all -
only very briefly when starting and stopping the engine. I checked it
over thoroughly underneath and everything is nice and tight. The noise
was probably coming from the engine itself. Maybe this is completely
normal? I previously had a Flymo L400 - a smiliar mower but much older
and with a different engine. No such noise from that (although it runs
much louder than the XL500)!

So does anyone else have the XL500? Do you get this same, slight
knocking noise when starting and stopping and is it normal?

Many thanks
Marc.c

On 10 May 2006 04:55:42 -0700, "Cokey" wrote:

Hi,

I hope this is the right group to post this question to - I couldnt
find a lawnmower specific group.

I have just purchased a Flymo XL500 petrol lawnmower. Upon starting it
for the first time yesterday, I noticed that for the first second or
two it makes a kind of knocking noise - as if the blade was slightly
loose or something. It also makes the same noise when stopping. While
running normally, cutting the grass, the noise is not there at all -
only very briefly when starting and stopping the engine. I checked it
over thoroughly underneath and everything is nice and tight. The noise
was probably coming from the engine itself. Maybe this is completely
normal? I previously had a Flymo L400 - a smiliar mower but much older
and with a different engine. No such noise from that (although it runs
much louder than the XL500)!

So does anyone else have the XL500? Do you get this same, slight
knocking noise when starting and stopping and is it normal?

Many thanks
Marc.c

Do you know the make and model of the engine, which would facilitate a
Google search for details?
Manufacturers have incorporated various features for easy starting and
stopping which include modified camshafts, decompressors etc. It could
be something like that coming into operation when starting and
stopping.

Engine is the Honda GCV 160. http://www.honda-engines.com/gcv160.htm

Ive googled but cant seem to find any info on the knocking noise.

On 11 May 2006 04:02:22 -0700, "Cokey" wrote:

Engine is the Honda GCV 160. http://www.honda-engines.com/gcv160.htm

Ive googled but cant seem to find any info on the knocking noise.

I see that's an overhead cam engine. I wonder if it incorporates some
kind of valve lifter/decompressor for starting and stopping. If it's
an engine wear knock it's usually worse under load. Some of these
single cylinder aircooled engines do rattle a bit when not under load.
There's nothing to insulate the sounds. It might not be anything to
worry about, but is there a local garden machinery dealer/servicer you
could ask?

Ive emailed the supplier - just awaiting a response.

"Jupiter" wrote in message
...

I see that's an overhead cam engine. I wonder if it incorporates some
kind of valve lifter/decompressor for starting

It does, to ease starting.

Just recieved a call from the suppler and he has confirmed that the
knocking noise is quite normal on start-up and shut-down so panic over!
Cheers
Marc.c

On 16 May 2006 02:22:22 -0700, "Cokey" wrote:

Just recieved a call from the suppler and he has confirmed that the
knocking noise is quite normal on start-up and shut-down so panic over!
Cheers
Marc.c

Old motorcycles with big single cylinder 4 stroke engines used a cable
operated valve lifter for starting and stopping. The idea when
starting was to decompress the engine, kick it over and then release
the lifter when it was spinnig over. It was supposed to burst into
life. They were hard to kick over under compression and there was
always the danger of it kicking back. The valve lifter was the only
way of stopping the engine (short of stalling it) because the old
magneto ignition didn't have any kind of switch. The valve lifter
used a make a sort of chuffing noise when operated.
Notice how the newer engines are much easier to pull-start then the
old ones. My Flymo RL400 has a B&S 'EZ-Start' engine which has a
profiled cam for starting, but my old Mountfield Rotovator with a much
earlier and bigger B&S engine has no starting aids at all and needs a
hard pull to get it going. You have to sort of feel the pull first,
like with the old motorbike kick starts, or you can get that nasty
pull back on the cord which is hard on the wrist!
Glad your mind's been put at rest about the noise.