Editing H engine (section)

== Design ==
{{refimprove section|small=yes|date=November 2019}}
The benefits of an H engine are the ability to share common parts with the flat engine upon which it is based, and the good [[engine balance]] which results in less vibration (which is difficult to achieve in many other types of four-cylinder engines).<ref>{{cite book| last= Willoughby| first=Vic | title= Classic motor cycles| year= 1989| publisher = Ivy Leaf| isbn= 0-86363-005-7}}</ref>

However, H engines are relatively heavy and have a high centre of gravity. The latter is not only due to the second crankshaft being located near the top of the engine, but also the engine must be high enough off the ground to allow clearance underneath for the exhaust pipes{{cn|date=December 2019}}.

The [[U engine]] layout uses a similar concept, placing two [[straight engine]]s side-by-side.