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[tunnie]

I've got an old lawn mower thanks to FatherT 

It's engine is a Briggs & Stratton Quantum XM 35, was a pig to start this year. So took off the float, cleaned it all up, fairly clean anyway, blast of carb cleaner in all its bits, new air filter and put it back together. Problem was the gasket on the air-intake was in a right state, so took it off for now. Re-assembled, without gasket.

Pull cord 3 times to prime, pull again and bang, straight into life.

Runs well, apart from after a while, the revs get very lumpy, it gets so bad it stops every so often. I'm thinking as it heats up, it's letting air in at the intake, more than it should, lack of gasket giving it lumpy hot revs?

Thinking of this:

http://www.ebay.co.uk/itm/Briggs-Stratton-Carburettor-Gasket-Set-fits-Max-and-Quantum-Engines-/221242600987

But can I use a liquid sealer? Or is better off going for one of these kits? 

[Andy B]

at £6 I'd go for the gasket kit. Other than that, if it's just the carb to manifold/head gasket you could use the time honoured cornflake packet 

[tunnie]

at £6 I'd go for the gasket kit. Other than that, if it's just the carb to manifold/head gasket you could use the time honoured cornflake packet 

I'm liking that idea, tunnie bodge     

[tunnie]

Seriously though, think will get kit. Cheers 

As can stash the head gasket for another day 

[Kevin Wood]

A little smear of hylomar or the aforementioned cornflake packet will be as good as anything. We're not talking about highly strung technology here!

Oh, and the running issue sounds like the float chamber might not be refilling, or is flooding. Check the float valve, float level and make sure the breathers to the fuel tank and float chamber aren't blocked. Could also be a blocked idle jet if it's difficult to start and then hunts while running.

[tunnie]

A little smear of hylomar or the aforementioned cornflake packet will be as good as anything. We're not talking about highly strung technology here!

Oh, and the running issue sounds like the float chamber might not be refilling, or is flooding. Check the float valve, float level and make sure the breathers to the fuel tank and float chamber aren't blocked. Could also be a blocked idle jet if it's difficult to start and then hunts while running.

Thanks Kevin 

If primed, it starts on the first pull and runs well. Problem is when hot, the revs hunt, as if you were in a car at idle reving the engine on the throttle.

I have taken the float cap off, clean it all up, the bolt with the little hole (that is the float valve?), blast of plus gas up into the 'float chamber' it appeared clean and moved ok.

Where is the idle jet? That said as above, it does start fine, hot running is problem 

[Kevin Wood]

Sounds to me like it could be the idle jet, then. Mine was the same - would start only after using the priming bulb generously, and would hunt once warmed up. If you hold the throttle closed against the stop it should run at a slow idle, but with a blocked idle circuit it will just stall.

This might help.

http://outdoorpowerinfo.com/repairs/tecumseh_carb_640017.asp

The idle jet comes through a small hole in the bowl retaining nut and up a passage drilled in the carb body to the progression holes just under the throttle plate and a jet somewhere in the bore. I think there's also an air bleed into it somewhere. A good blast of carb cleaner followed by some compressed air should clean it. Might need to soak the carb in carb cleaner first, though.

[tunnie]

Awesome link, perfect. Thanks     

I cleaned small hole in the retaining nut, must be a blockage further up. 

[aaronjb]

Not carb cleaner being used for it's actual intended purpose?

Shock, horror!

[omega3000]

Bloke next door was swearing at his petrol mower , yanking the pull cord for half an hour and all it did was pop and bang  Ah its good to have gravel garden 

[Taxi_Driver]

My mower doesnt have an idle jet .....

You press the bulb several time to flood the carb.....then keep the lever pulled back on the push bar.....and pull the cord....it usually goes first time with loads of white smoke to start with on full throttle and stays on full throttle until you release the the lever which not only kills the engine but puts a brake on the blade 

[Rods2]

I've got an old lawn mower thanks to FatherT 

It's engine is a Briggs & Stratton Quantum XM 35, was a pig to start this year. So took off the float, cleaned it all up, fairly clean anyway, blast of carb cleaner in all its bits, new air filter and put it back together. Problem was the gasket on the air-intake was in a right state, so took it off for now. Re-assembled, without gasket.

Pull cord 3 times to prime, pull again and bang, straight into life.

Runs well, apart from after a while, the revs get very lumpy, it gets so bad it stops every so often. I'm thinking as it heats up, it's letting air in at the intake, more than it should, lack of gasket giving it lumpy hot revs?

Thinking of this:

http://www.ebay.co.uk/itm/Briggs-Stratton-Carburettor-Gasket-Set-fits-Max-and-Quantum-Engines-/221242600987

But can I use a liquid sealer? Or is better off going for one of these kits? 

Check how clean the petrol tank is and any filter in there, as they have a tendency to collect grass cutting over time which as you use the mower migrate to the fuel filter and block it, when the engine stops they are released from the filter and when you start it the cycle starts again.

[Sir Tigger KC]

Electric mowers are a bit poofy, but by the time you guys have got yours going I've plugged in, whipped around and have my feet up admiring my handiwork! 

[Kevin Wood]

Electric mowers are a bit poofy, but by the time you guys have got yours going I've plugged in, whipped around and have my feet up admiring my handiwork! 

.. unless you maintain your mower, in which case it starts quicker than it takes to get the extension lead out.

[Sir Tigger KC]

Electric mowers are a bit poofy, but by the time you guys have got yours going I've plugged in, whipped around and have my feet up admiring my handiwork! 

.. unless you maintain your mower, in which case it starts quicker than it takes to get the extension lead out.

I've got an Omega, I don't want a mower that needs constant fettling as well!