Ask the Editors: Engine Swap Concerns
Close cousins.
So, My question is this: Will a 1993 300cc engine fit the 87?
Any thoughts appreciated. Hondoe
This is a fairly simple question with a complicated answer but we’ll get to that. The short answer is yes, the newer 300CC engine (actual displacement of 282cc) can be made to fit the 87 chassis but it is not a plug & play swap.
The first item in need of contemplation before considering such things is whether or not the 250X’s engine is in decent shape. If so, you would gain literally no performance by performing the 300EX engine swap. About the only gain to be had in doing so would be transitioning from a kick-start model to electric.
If the 250X’s engine is shot- then there becomes a bit more incentive to attempt the motor transplant but as we said above, despite being built from the same rolling chassis, there were enough minor tweaks in transitioning from 250X to 300EX to make the process more work than one would expect. Among these a different wiring harness, battery box/ frame tabs for the 300EX, bracket for the voltage regulator etc.
If you’re handy with a welder and don’t mind customizing a few bits to make the swap work, the engine itself will use the same motor mounts/ exhaust routing. However, the work you describe the 300EX needing sounds mostly cosmetic by nature- remember that the 250X’s plastics, bars, seat and so on can also be mounted to the 300EX’s chassis as well.
