I've an old Enya 40 ss which was running fine, but now fails to slow run. I have checked the fuel lines and filters, exhaust pressure line, changed the glow-plug to no avail. The needle valve appears to be adjusting the main throttle mixtures OK. She starts OK and the compression feels normal. Can anyone tell me the function of the two spring-loaded adjustment screws on the carburettor block. I don't think they have been touched since the motor was running OK, but the one nearest the cylinder seems to be quite loose. Thanks, Ernie