Help needed with engine displacement size ??

[Jonny The Goat]

Hi, can someone confirm I have got this calculation using a online displacement calculator right. I bought a old 30s bike some years ago with a incorrect for bike engine in but still have not managed to ID the make of engine or the size. I was told by last owner they thought it was a 250 and also they thought it was a Villiers 250R. I have discounted that. it is a 2 stroke twin port combined barrel and head. Anyway I today pulled the engine out as wanted to get damaged fins repaired and a hole by one of the screw on exhaust outlets fixed. I have measured the bore at 68.5mm and the piston from its very bottom of stroke to very top of stroke travels 75mm. According to the online calculator I used it is a 276cc ? Have i got this right ? I was very sceptical about it even being a 250cc as it looks a quite small engine. With the angled top on the piston does this have any bearing.
  Cheers Jon

 https://www.revetec.com/Calculators/Engine_Displacement_Calculator-2.htm

[L.A.B.]

I have measured the bore at 68.5mm and the piston from its very bottom of stroke to very top of stroke travels 75mm. According to the online calculator I used it is a 276cc ? Have i got this right ?

Yes.

With the angled top on the piston does this have any bearing.

No.

[murdo]

I get 276.43cc, so yes you are correct.