I browsed the forum without joy.

Will MC 18 barrels fit a MC 21 crank casing without any alteration to mounting arrangement and port aligning?

What will be the consequence if the exhaust port measurement to top is decreased from 28mm to 26mm?

Love the smell of 2 stroke in the morning.

Howzit , you can bolt on 16 or 18 barrels , no problem . Port height -- if you measurement is less than 28mm , you loose fuel mixture through the exhaust port . Something with port timing