Complex sentence: He designed a counter-balanced crankshaft as part of the tuning work on the engine, before EX120's first visit to Montlhéry in December 1930, when it took several records at speeds up to 87mph.
Split into simpler sentences: He designed a counter-balanced crankshaft as part of the tuning work on the engine, before EX120's first visit to Montlhéry in December 1930. It took several records at speeds up to 87mph.