88 motor is fairly similiar to later 89/on motors {crank/transmission/ port timing
top of exhaust port is about 2mm lower than 89on but overall is got more area and alot cleaner port roof
the 89on centre kipps is pretty crude and may and also has issues with cracks in exhaust bridges
main differance on the 88 motor are
differant top end/ larger and heavier more water a kips capacity no centre kipps,
differant intake area and top reeds run closer to piston than 89on{not good}
bigger crankcase volume {differant cases with no centre kipps hole ] holes in 88crank could be plug for less volume
lighter flywheel /slight differant timing 2degree
current building a 88 will post pictures when i get off my ass in gear