OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs small engine carby

What is it that makes these work and what is it that prevents them from working. This one I have here is brand new, I fitted it to the tank, the primer bulb squirted twice and then nothing. Obviously something is blocked, but both strainers are clean. Any thoughts?

Did you have the tank fitted to the engine?

These 'Pulsa-Jet' carbies use the intake pressure pulses, acting on part of the diaphragm, to pump fuel up to the well in the top of the tank. That well is a 'constant level' device, analogous to a conventional float/needle setup.

From there, the fuel is drawn up through the main jet by the partial vacuum at the carby venturi, as with a conventional float carby.

So it needs the pump to keep it topped up - excess fuel just overflows back into the tank. As the well/chamber doesn't hold much fuel, it will empty quickly if the pump isn't working. Also, it can take quite a few pulls of the starter to fill it up from empty, e.g. when the tank has been off the engine for cleaning/overhaul.

2 things Norm, when starting from empty tank you'll either need to fill tank to the top or prime it a lot more. they use a spring/Diaphragm with port flaps for in & out arangment.
There should be a small dish in the tank for the shorter pipe, I found it needs to have fuel in it.

Thanks Gadge and Paul, I have been swapping a lot of these carbs and tanks around, cleaning them and getting them working, but I bought this new carb and when I fitted it I only go 2 squirts out of it and now nothing. There is something blocked in the carb, what is under the strainer on the long leg, I assume this is the main jet, is there anyway to remove the strainer without damaging it?

G'day all,
The long pipe is the pickup tube for the pump. Dunno if it's detachable on these plastic body carbs, but if the strainer end is hex shaped it should unscrew.

With the carb off the tank, it should be possible to blow air up it and feel it coming out at one of the diaphragm flap valve locations.

The short pickup is where the main jet lives, with its own strainer.
There are only three fuel passages in these carbs; pump in, pump out and main jet - so it should be possible to work it out, barring major manufacturing faults.

I watched a youtube vid on how to remove. they gently warmed the plastic where it meets the brass tube (which screws out) and pull the plastic part off same for putting it on...
don't melt it.

Gadge, I think you might be right, being a new Chinese carby and untested on a running motor I figure a manufacturing fault. I used to get that often with Enfield carbys from India, Indian parts were terrible compared to Chinese parts

Boy I must be drunk as I can't see the carby clearly this morning. Only 1/4 glass of homemade wine last night.

You also may need to remove the primer bulb if I recolonizing the right carby. Behind it is a seat, steel ball and spring. This passage could be the problem as I have seen a few stuck closed or have foreign material in there and would not prime.

Going to get some coffee to see if I see clear. NormK just back off with camera a little I you too close to focus but it could be me too.

Sorry AVB, my bad I must have moved as I took it, coffee is not going to solve it I will take another pic in the morning just for you. When I first got the carb a couple of weeks ago I put it on a motor and as I said the primer only squirted twice, I put a dribble of petrol into the carb and the motor started and ran fine. Yesterday I tried it on another motor in a different tank, primer didn't work and even with a dribble of petrol in the carb, not a murmer from it, not even a spit back. I fitted another carby and tank and the motor now runs fine

Sorry AVB, life got in the way for the last couple of days but here's a couple of better pics