Editing Straight-four engine (section)

== Usage in motorcycles ==
{{See also|Motorcycle engine}}
[[File:Honda CB750 Engine.jpg|thumb |1970 [[Honda CB750]] engine]]

Belgian arms manufacturer [[FN Herstal]], which had been making [[FN (motorcycle)|motorcycles]] since 1901, began producing the first motorcycles with inline-fours in 1905.<ref name=cleveland>{{cite web |url=http://www.motorcycleclassics.com/classic-american-motorcycles/cleveland-motorcycles-zmsz17mjzhur |last=Siegal |first=Margie |title=The Same, But Different: 1927 Cleveland 4-45 and 4-61 Motorcycles |magazine=[[Motorcycle Classics]] |access-date=2017-06-20 |date=May–June 2017}}</ref> The [[FN Four]] had its engine mounted upright with the crankshaft [[Longitudinal engine|longitudinal]]. Other manufacturers that used this layout included [[Pierce-Arrow|Pierce]], [[Henderson Motorcycle|Henderson]], [[Ace Motor Corporation|Ace]], [[Cleveland Motorcycle Manufacturing Company|Cleveland]], and [[Indian Four|Indian]] in the United States, [[Nimbus (motorcycle)|Nimbus]] in Denmark, Windhoff in Germany, and [[Wilkinson Sword#Motorcycle production|Wilkinson]] in the United Kingdom.<ref name="CW4runners">{{cite journal |last= Edwards|first= David|date=August 1997|title= Four-Runners |journal= [[Cycle World]]|volume= 36|issue= 8|pages= 42–43|location= Newport Beach, CA USA|publisher= Hachette Filipacchi Magazines|editor1-first= David|editor1-last= Edwards|issn= 0011-4286|access-date= 2013-09-21|url= https://books.google.com/books?id=QGMMRS3b0KQC|ref= CW4runners}}</ref>

The first across-the-frame 4-cylinder motorcycle was the 1939 racer [[Gilera#History|Gilera 500 Rondine]], it also had double-over-head camshafts, forced-inducting supercharger and was [[Radiator (engine cooling)|liquid-cooled]].<ref name=first>{{cite web |url=https://www.motorcycleclassics.com/classic-italian-motorcycles/classic-gilera-motorcycles/1939-gilera-500-rondine-zm0z18jfzhur |last=Hamish |first=Cooper |title=Radical Rondine: 1939 Gilera 500 Rondine |magazine=[[Motorcycle Classics]] |access-date=2018-04-13 |date=January–February 2018}}</ref> Modern inline-four motorcycle engines first became popular with [[Honda]]'s [[SOHC]] [[Honda CB750|CB750]] introduced in 1969, and others followed in the 1970s. Since then, the inline-four has become one of the most common engine configurations in street bikes. Outside of the [[cruiser (motorcycle)|cruiser]] category, the inline-four is the most common configuration because of its relatively high performance-to-cost ratio.{{Citation needed|date=September 2013}} All major Japanese motorcycle manufacturers offer motorcycles with inline-four engines, as do [[MV Agusta]] and [[BMW motorcycles|BMW]]. BMW's earlier inline-four motorcycles were mounted horizontally along the frame, but all current four-cylinder BMW motorcycles have [[transverse engine]]s. The modern [[Triumph Motorcycles Ltd|Triumph]] company has offered inline-four-powered motorcycles, though they were discontinued in favour of [[Triumph Triple|triples]].

The 2009 [[Yamaha R1]] has an inline-four engine that does not fire at even intervals of 180°. Instead, it uses a [[crossplane]] crankshaft that prevents the pistons from simultaneously reaching top dead centre. This results in better [[secondary balance]], which is particularly beneficial in the higher rpm range, and "[[big-bang firing order]]" theory says the irregular delivery of torque to the rear tire makes sliding in the corners at racing speeds easier to control.

Inline-four engines are also used in [[Grand Prix motorcycle racing|MotoGP]] by the [[Suzuki MotoGP|Suzuki]] (since [[2015 MotoGP season|2015]]) and [[Yamaha Motor Racing|Yamaha]] (since [[2002 Grand Prix motorcycle racing season|2002]]) teams. In [[2010 Grand Prix motorcycle racing season|2010]], when the four-stroke Moto2 class was introduced, the engines for the class were a {{cvt|600|cc|cuin|1}} inline-four engine made by [[Honda Racing Corporation|Honda]] based on the [[Honda CBR600RR|CBR600RR]] with a maximum power output of {{cvt|110|kW|hp|round=5}}. Starting in [[2019 Moto2 season|2019]], the engines were replaced by a [[Triumph Motorcycles Ltd|Triumph]] {{cvt|765|cc|cuin|1}} [[straight-three engine|triple engine]].