Briggs & Stratton 4-stroke mower

Gib Bogle · 2011-07-31T05:22:00+00:00

My trusty old mower is no longer trusty. It starts OK, and runs for a couple of circuits of the lawn, then stops dead. The stop is so sudden it almost seems electrical, but in other respects it's as if the fuel in the carburettor float chamber has been used up and not replenished - but of course there is no float chamber, and the fuel system looks childishly simple. The electrics are so simple - no moving parts except the magneto - that it's hard to see what could go wrong there either. Maybe there is something about the fuel system that I don't understand. I've taken all the fuel-related bits off, and when I feel inspired I'll take them apart and clean everything. Meanwhile, perhaps someone with experience can suggest what I should be looking for. The sparkplug is new, by the way. It does look rather sooty, but not at the business end (close to the gap).

Jul 31, 2011 24 Replies

Rate this thread:

Pete Shew 14 years ago

No, no manual fuel tap, just the solenoid which stops the fuel leaving the float chamber via the main jet. It was probably developed as a nasty fix for when users turn off the engine at full throttle and are startled by the bangs from the exhaust.

For some reason mine got weak when warm and couldn't pull the needle down against the spring so shutting off the fuel. The solenoid seems difficult to disassemble without damage and as a new one is close to £100! it seems that a 10p set screw was the correct fix.

Pete

Vote

Gib Bogle 14 years ago

To wrap this up: my trusty, incredibly simple, old B&S is now trusty again. I thoroughly cleaned the carb and tank, changed the oil, and then did the lawn with no sudden conking out. There was no obvious problem anywhere - no water in the oil or petrol, little sediment in the tank - but whatever it was it seems to be fixed. I didn't need to check the points, but should take a look some time. Thanks for all the advice and interesting comments.

Vote

The Natural Philosopher 14 years ago

Classic bit of grit in the carb behaviour ....

fit fuel filter?

Vote

Gib Bogle 14 years ago

Where? The carb is bolted on the top of the petrol tank. A tube sticks down into the petrol. It has a gauze filter on the end.

Vote

The Natural Philosopher 14 years ago

Ah. That should have been enough.

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required