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.