20. What would make my engine start hard, but then run perfectly OK once it starts?

Whenever an Atomic-4 starts hard, but then runs OK after it starts, it is almost always the case that the choke is not closing completely, and/or a person's starting technique itself is less than perfect.

Due to the updraft design of the carburetor, the engine relies on a spring-loaded poppet valve on the choke disk to allow just the right amount of air to be drawn in through a completely closed choke valve for a good crisp start. If the choke valve is open even a slight bit, hard starting will almost surely result.

Your choke cable should pull almost effortlessly, so that the resistance you eventually feel as you continue to pull the the choke knob is in fact the choke valve itself closing. If you're feeling a lot of resistance within the cable, you'll run the risk of not quite getting the choke valve completely closed, or you may actually damage the choke assembly on the carburetor by pulling too hard on the choke lever after the choke is closed.

It is well to point out here that it's almost impossible to flood the Atomic 4. Even if fuel is seen to be pooling in the mouth of carburetor, the choke must be fully closed for a good clean start.

Here are a few tips on starting technique:

1) "Pumping the throttle" is totally ineffective as a starting technique for the Atomic-4. Since there is no accelerator pump within the carburetor, pumping the throttle has absolutely no effect on anything in terms of supplying more or less fuel to the engine.

2) If your engine tries to start, but falters and stops as soon as you stop cranking on the starter, it is likely simply not getting enough fuel to work itself out of the idle range and into the lower range of the main discharge nozzle of the carburetor (which occurs around 1000 RPM). After an engine is warmed up, it will tend to start OK in idle, but cold engines seldom will start and run within the idle range. They need to start and warm up in the lower range of the main discharge nozzle before they can be brought back to idle.

3) The best setting for the throttle during starting is solidly off of the idle stop, so as to uncover both idle ports and get you into the "off idle" range of operation. It's somewhat better to err on the high side in terms of throttle setting. If your engine ends up racing the instant that it starts, you can back off a little on the throttle setting during future starts. - Updated: January 3, 2004