A process for controlling a yield of an isomerization zone. Prior to entering the isomerization zone, C6 cyclic hydrocarbons are removed from a feed stream. Disproportionation reaction selectivity is observed which produces valuable C3 hydrocarbons and C4 hydrocarbons. Also, a higher ring opening conversion of C5 cyclic hydrocarbons is observed. The disproportionation reactions and the ring opening reactions may be selectively controlled by adjusting an amount of C6 cyclic hydrocarbons passed into the isomerization zone.