I have a 2hp B&S from an old edger. The engine runs well and not too hard to start after about 3 pulls. I have noticed though that with the breather off, as I am trying to start it, I see little puffs of smoke (fuel vapor) come back out the carb while its running. It sucks right back in on a downstroke though. Also, if I choke with my palm on the carb, I can feel the pressure pulse. Is this normal or do you suppose I have a leaking intake valve? I wasn't sure if perhaps the timing is just enough BTDC that I am seeing this because the valve hasn't quite closed yet.
Do I have a leaky intake valve or is this normal?
- Thread starter FrankR
- Start date
Briggs uses what is called "Easy spin" on many of thier engines. What it amounts to is there is about .01 of material on the Intake lobe of the camshaft. This helps releive compression when the engine is started. It holds the intake valve slightly open for a few degrees of crankshaft rotation. The air /fuel mixure reverberates at really slow speeds such as when the pull start is being used. It has little affect at higher rpms. All of this is written in the back of the Briggs engine service manual. When the Intake valve recedes in the seat it can tend to amplify this condition. Make sure your valve lash is up to spec. A little back blow is normal. Total loss off low rpm responsivness is a sign of a problem. Hope this helps.
A little blow back is normal on a flat head. Its what makes the fuel pump work(B&S motors, tank mounted below carb)....Pull the spark plug, put your thumb over the hole, pull the cord. if it blows your thumb off the hole You should be fine....... Lapping the valves wont hurt and its reall easy on a flathead,good luck....
