Never seen a manual but try this:
If the fuel tank is under the carb, the carb has to suck its fuel up a pick up tube within the tank. The pick up tube is usually plastic and has a very fine filter which very easily gets clogged up.
Separate the carb and the tank (first take a photo of the spring locations etc) Remember that the dismantling process may well cause the obstructing debris to fall away from the filter. Dont be fooled- flushout the tank and blow down the pick up tube from the carb side to free any gunge else anything left behind will only get drawn up to the filter within the first 10 mins of use.
GB in Wales
February 2013