ORIGINAL: freeair
yes if your talking about the black plastic type fuel inlet to caby, your engine must be getting very hot to where the carby is positioned, work out some type of ducting so better air flow gets to the carby as well as the cylinder .
No, it is not the fuel supply pipe, it is the pipe that allows the carb to suck fuel from the tank. It was the black plastic nipple at the engine end that softened & fell off. The nipple at the carby end is fine. Plenty of air circulation, as the model was previously fitted with a Saito 180 & the much of the lower cowl is cut away.
To my mind, any plastic attached to the engine cylinder is likely to melt.
The weather is getting hot here. It was in the low 40'sC the day it happened. Maybe that didn't help.