Viking mower with Briggs MB 253.1T has me baffled

[Hughtheboatman]

Hi, I'm new here after having just wasted several hours on YouTube seeking enlightenment.

A neighbour has asked me if I can help her get her Briggs-engined Viking mower going again. I've been messing around with engines ranging between tiny model aeroplane units under 1 cc up to 10,000 HP marine diesel engines over the past 60+ years, so this isn't my first rodeo :-)

She refuelled the machine a couple of days ago and it wouldn't start afterwards. I don't know the age of the fuel. I had a look today and got it to fire by squirting fuel into the choke flap but it wouldn't pick up. This evening I persevered and got it to run for 15 minutes in 'static mode', but as soon as I tilted it it cut out and wouldn't restart without manual priming in the choke hole. This engine doesn't have a priming bulb or manual choke. I've had the starter off and studied the thermal choke link and other control rods but can't see anything wrong.
I really don't want to dismantle the plastic carburettor because it looks a bit on the flimsy side but maybe that's where the problem lies.

In short, it will run OK until I put any changing load on it, and which point it just quits.

Any advice will be very welcome. Thanks, H.

[Mick]

Hi Hugh, and welcome to TGMF.

Well it certainly sounds like it has a carb issue, so I think you'll eventually have to remove it.  They are really easy to remove and clean.  Just check you have a flow of fuel from the tank once it's removed.

1: Remove top cover via the three top cover screws.
2: Lift fuel tank out of its mounting slots and just leave it hanging.
3: Remove air filter cover followed by the air filter element.
4: Remove the two very outer screws from the air filter backplate.
5: Pull off the carburettor from the inlet spigot.
6: Gently twist carb until you can remove the throttle rod from the throttle shaft.
7: Twist back slightly and remove the choke rod.

Remove the two screws from bottom of carb (fuel bowl) You can prise out the white jet module and give everything a good clean, then reassemble in reverse order.

here's some videos which might help, though I don't usually take off the whole filter backplate from the carb unless I need to.

[Hughtheboatman]

Thanks, Mick.
That worked a treat! There was about a teaspoon of water in the carb bowl but also some dirt in the jets area. After re-assembly it started on the 5th pull :-)

Right after opening the carb I realised that there was the drain plug in the bottom of the bowl - I might try that short-cut first, next time.
Cheers, H

[Mick]

Glad it worked out good in the end. 

I was going to mention the bung, I would do this if someone had put diesel instead of petrol in the tank etc, and it's a quarter turn bayonet style bung which requires a rather large Allen key to remove it, some don't have such keys.

To be honest it literally takes a minute to get the carb off and you can then check and clean it properly like this.  On he upside you won't be so worried about dismantling one of these plastic carbs again.