Just gone though this all again, should be a different animal since when I last had a ride in it for sure.
What does 87mm bore with 86mm crank put it into total engine displacement wise?
(Bore/2)^2 x Pi x stroke x 4 = displacement
(8.7/2)^2 x 3.14 x 8.6 x 4 = 2043.9 Cubic Centimeters