Sorry if i have posted this to the incorrect place, I am just new to the site...

I have a briggs stratton lawn mower which i bought from B&Q about 18 months ago...

its worked perfectly until i lent it to moy brother who has just moved into a house with an overgrown 80ft garden! now when i try to use it it seams to surge (i.e. nearly cuts out then revs then nearly cuts out again) i`ve cleaned all the gras that I can see and also removed the air filter and cleaned that. it seams to be using loads of petrol...

the little arm that controls the revs is going backwards and forwards all the time trying to keep the revs up. (sorry thats probably not the technical term for it!!

any advice you can give would be great!

cheers

On Tue, 16 Aug 2005 10:44:06 +0100, hardyboy wrote:

now when i try to use it it seams to surge (i.e. nearly cuts out
then revs then nearly cuts out again) i`ve cleaned all the gras that
I can see and also removed the air filter and cleaned that. it seams
to be using loads of petrol...

They do that when hunting badly like yours. I suspect it is either a
damaged or slightly misplaced carburetor diaphragm. This is found
between the tank and the carb, it functions as fuel pump and a couple
of one way flap valves.

I had just your symptoms on my B&S engined mower this season. Took the
carb/tank assembly off and separated the carb from tank. One of the
little flap valves was tucked down into the hole it should cover.
Refitted making sure that the diaphragm was positioned so that the
flap had maximum chance of covering the hole and minimum of going back
down and the mower has been fine since.

Things are bit delicate and fine in there so be careful...

--
Cheers
Dave. pam is missing e-mail

On Tue, 16 Aug 2005 15:41:41 +0100 (BST), "Dave Liquorice"
wrote:

On Tue, 16 Aug 2005 10:44:06 +0100, hardyboy wrote:

now when i try to use it it seams to surge (i.e. nearly cuts out
then revs then nearly cuts out again) i`ve cleaned all the gras that
I can see and also removed the air filter and cleaned that. it seams
to be using loads of petrol...

They do that when hunting badly like yours. I suspect it is either a
damaged or slightly misplaced carburetor diaphragm. This is found
between the tank and the carb, it functions as fuel pump and a couple
of one way flap valves.

I had just your symptoms on my B&S engined mower this season. Took the
carb/tank assembly off and separated the carb from tank. One of the
little flap valves was tucked down into the hole it should cover.
Refitted making sure that the diaphragm was positioned so that the
flap had maximum chance of covering the hole and minimum of going back
down and the mower has been fine since.

Things are bit delicate and fine in there so be careful...

You're describing the PulsaJet carb which is an older design. A lot
of newer engines have the PulsaPrime carb which has the big rubber
bulb to press 3 times for pre-starting priming. They don't have that
little diaphragm. The usual cause for fuel starvation (and hunting)
with them is partial blockage of the screen on the dip tube in the
fuel tank. Remove tank and carb complete, separate the carb from the
tank and check the end of the dip tube. Clean as appropriate. Just
fixed the problem on a Flymo RL400. My Mountfield Rotovator, however,
has the same carb (PulsaJet) as yours. That needed a new diaphragm.

On Wed, 17 Aug 2005 07:57:23 +0100, Jupiter wrote:

You're describing the PulsaJet carb which is an older design.

This is no more than 3 years old. Can't a aresed to look for the full
engine number and work out the manufacture date.

A lot of newer engines have the PulsaPrime carb which has the big
rubber bulb to press 3 times for pre-starting priming. They don't
have that little diaphragm.

It has a press 3 times primer for cold engine start, it has a
diaphragm. It's not what I would call little, it also functions as a
gasket between the carb and tank from memory about 2 x 2.5".

--
Cheers
Dave. pam is missing e-mail

cheers for that Dave,

i`ll have a play around with it tonight! i have to say engines aren`t my speciality! i`m more of a cider drinking TV watcher!

if you hear anything in the news about man in lawn mower tragedy then you`ll know who it was!!

cheers again!!

On Wed, 17 Aug 2005 09:10:40 +0100 (BST), "Dave Liquorice"
wrote:

On Wed, 17 Aug 2005 07:57:23 +0100, Jupiter wrote:

You're describing the PulsaJet carb which is an older design.

This is no more than 3 years old. Can't a aresed to look for the full
engine number and work out the manufacture date.

Date of manufacture doesn't determine age of design!

A lot of newer engines have the PulsaPrime carb which has the big
rubber bulb to press 3 times for pre-starting priming. They don't
have that little diaphragm.

It has a press 3 times primer for cold engine start, it has a
diaphragm. It's not what I would call little, it also functions as a
gasket between the carb and tank from memory about 2 x 2.5".

Ah, so your diaphragm fits between the tank and carb, not under a
plate on the side of the carb. So yours is a PulsaPrime. The PulsaJet
has a 'little' diaphragm with 2 flap valves under a side plate and 2
dip tubes into the fuel tank. One draws from the bottom of the tank
and pumps into a secondary cup inside the tank and the engine is
supplied by the other one drawing from the cup so it doesn't need a
separate priming mechanism. The idea is that the cup is always full
so that the level of fuel in the main tank doesn't affect the
performance of the engine.

Still worth checking checking the filter screens on the dip tubes,
whatever the type. There's a lot of vibration with those engines and
any sediment will inevitably be stirred up.

On Wed, 17 Aug 2005 11:02:11 +0100, hardyboy
wrote:


cheers for that Dave,

i`ll have a play around with it tonight! i have to say engines aren`t
my speciality! i`m more of a cider drinking TV watcher!

if you hear anything in the news about man in lawn mower tragedy then
you`ll know who it was!!

cheers again!!

Always disconnect the spark pliug lead and tie it out of the way if it
it still lies close to the plug.