question about motor size on drr

[Bodie1]

I have a guy wanting to sell me a motor off a drr he says its a 90cc how can I tell visually? Are there any marking or numbers on it. He says he cant find any. Any help would be appreciated. Thanks..

the 90 will have a round head the 50 70 has like a sqaure with a point at the top

[Bodie1]

Hey Thanks for your help racers 3, I sure appreciate it.