briggs & stratton lawn mower problems

Sorry if i have posted this to the incorrect place, I am just new to th
site...
I have a briggs stratton lawn mower which i bought from B&Q about 1 months ago...
its worked perfectly until i lent it to moy brother who has just move into a house with an overgrown 80ft garden! now when i try to use it i seams to surge (i.e. nearly cuts out then revs then nearly cuts ou again) i`ve cleaned all the gras that I can see and also removed th air filter and cleaned that. it seams to be using loads of petrol...
the little arm that controls the revs is going backwards and forward all the time trying to keep the revs up. (sorry thats probably not th technical term for it!!
any advice you can give would be great!
cheer
-- hardyboy
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On Tue, 16 Aug 2005 10:44:06 +0100, hardyboy wrote:

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 snipped-for-privacy@howhill.com
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On Tue, 16 Aug 2005 15:41:41 +0100 (BST), "Dave Liquorice"

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

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.

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

Date of manufacture doesn't determine age of design!

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.
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cheers for that Dave,
i`ll have a play around with it tonight! i have to say engines aren` my speciality! i`m more of a cider drinking TV watcher!
if you hear anything in the news about man in lawn mower tragedy the you`ll know who it was!!
cheers again!
-- hardyboy
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On Wed, 17 Aug 2005 11:02:11 +0100, hardyboy

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