Can any bicycle be retrofitted with a four-stroke engine?

Any type of bicycle can be retrofitted with a four-stroke engine, even folding and mountain bikes. As of 2015, a quality four-stroke bicycle engine kit ranges in price from $500 to $700. Typical kit installation for a belt drive engine kit is about 30 minutes.

Depending on the rider's needs, bicycles can also be fitted with a two-stroke engine. A two-stroke engine offers a faster top speed which is better for commuting, while a four-stroke engine is better for lower gears and pulling a trailer or frequently climbing hills. Another consideration is that a four-stroke engine uses gas straight out of the pump, while a two-stroke requires the gas be mixed with two-stroke mixing oil.