That's a point, I'd assumed these things aren't sports cars but it must be worth trying. I'm not sure if I want to add octane booster to everything that's not running perfectly (that'll be everything then) but it must be worth trying it to prove a point.
I've managed to get the right filter elephant for it but the filter box is missing it's lid. What my dad's done is stick a bit of sheet steel over it with half a dozen 3mm holes in it, I've no idea how much air it's meant to get but overfuelling on full power might explain it's feebleness. Can't remember it smoking though...
B&S engines seem particularly good at filling the filter with oil if you tip them up at all, so cleaning off the bottom of a mower can be a pain in the bum. The oil travels up the crank case breather pipe and tips straight into the carb, so if it doesn't soak into the filter it chucks a load of oil into the cylinder so it smokes like buggery next time you start it (right or left, although I suspect if you tip it to the left the oil stays in the pipe ready for the next time you start it, whereupon the vacuum sucks it into the carb). B&S are pretty good otherwise (carb diaphragms aside), I've got one here that came off a friend's lawnmower, it's crank seal has been leaking for years so it's spent a lot of time with very little oil in it, it has almost no compression but, before the mower it was attached to rotted away, it still chugged along merrily.
I've just been shopping (largely because everything I wanted to use was put back in the cupboard empty

) and for the first time I had someone buttonhole me to ask what the RAV was like, it was some old boy in an old Aldi that parked up behind me. So I told him how much I like* it. I don't suppose he'll be buying one of those now
