My 1961 C15 starts easily but the moment you touch the throttle it immediately dies. It will tick over for 10 to 15 seconds and the stop it will restart easily but the same thing will happen again touch the throttle and it will stop. I will do this routine 5 or six times and eventually you can blip the throttle and it will run ok but even when running normally there is always a slight hesitancy from no throttle to any throttle opening.
I have adjusted the slow running jet but it has no effect on this problem.
What is the spark like?
Should be a good blue crack at the plug
I would think that one of your carb jets is blocked. Most likely the main jet, either dirt of a blob of water, stopping the flow of fuel.
Invest in a can or two of carb cleaner, and remove the carb, and clean all the passageways with the spray.
Thanks for replies. I will strip the carb and remove and clean the jets. I have a friend with an ultrasonic cleaner and will ask him to use it on the carb body.
The spark is good and I only get the problem at low throttle so feel it is carburation rather than ignition.