Malaguti f15..problem..

[S.tranter]

hi I have malaguti phantom f15, which I have had from new .it's spends a lot of time stored..starting it periodically, it now start up but then cuts out, it has fresh fuel and a new battery..leave it for a couple of minutes, and it starts then cuts out..it has only achieved at total of 750 k..20 odd years ..any help appreciated..regards Steve