Originally Posted by dentvet
102x84.5 is 690 specs
so 102 bore with 55 mm stroke is 450 cc
so they will lengthen the rod and drop the wrist pin to make up 30 mm in stroke. It sounds like they are doing mostly rod lengthening because they are going to use the same basic piston as a hi comp 690 piston (close to stock wrist pin location therefore)
This should keep the scrutineers scratching their scalps
Yer that is one way of doing it.
As i said it will be interesting.
Scrutineers should have a capacity checker.