Join Date: Sep 2003
Location: Auckland New Zealand
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Don't know much about Atomic whatevers but I have been around petrol engines for several decades so maybe I can help.
RPM surge is almost certainly a fueling issue and conmtrary to popular belief, it is not always caused by the engine "running out of fuel" only. It is often caused by a mixture momentarily too rich for proper combustion.
I don't think it will be caused by a choke unless the butterfly is allowed to fluctuate on and off. Chokes are generally permanently positioned and the engine reacts more permanently to the condition.
It is more likely to be a float level issue in which the float is either too low (insufficient fuel supply, blocked lines or filter, etc) or too high (stuck needle'n'seat, float contains fuel, sides of chamber dirty causing float to stick, dirt under needle, etc).
As said above, there are possible issues with the fuel pump as well so check the flow at the incoming line.
Have the carb serviced by someone who (really) knows how.
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