fuel blow back whats the cause?

[brianc]

the piston is an unmodified mahle,

brian.

[Monty]

Mine was a bog standard unmolested 185 Mugello. It had run the same setup for 3 years. After having the barrel replated I started to have problems starting warm. Carb rubber full of petrol and when it was off I noticed the amount of spit back was massive. I went for thicker and then thinner base gaskets variable timing and in the end just bought a new carb. sorted.you need to check all the obvious like worn rings and carb needles