Editing V-twin engine (section)

===Longitudinal engine===
A less common arrangement is to mount the engine longitudinally. An advantage of this arrangement is that both cylinder heads can protrude into the air stream, so they can each receive the same amount of cooling (for air-cooled engines).<ref name=Coombs>{{Citation |last1=Coombs |first1=Matthew |last2=Haynes |first2=John |last3=Shoemark |first3=Pete |title=Motorcycle Basics |edition=2nd |publisher=Haynes |year=2002 |page=1•31 |isbn=978-1-85960-515-8 |url=https://books.google.com/books?id=D0DhHAAACAAJ }}{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Also, the transmission being located behind the engine is easier to fit within a typical motorcycle frame and, for shaft-drive motorcycles, a 90° [[bevel gear]] is not needed at the start of the driveshaft.

As per all longitudinal engines, a disadvantage is that the torque reaction will twist the motorcycle to one side (such as on sharp acceleration/deceleration or when opening the throttle in neutral) instead of shifting the weight balance between the front and rear wheels. However, many modern motorcycles reduce this effect by rotating flywheels or [[alternator (automotive)|alternator]]s in the opposite direction to that of the crankshaft.<ref name="MotoCruiserApr2000">{{cite web| url = http://www.motorcyclecruiser.com/roadtests/sport_cruisers_comparison/index.html| title= Sport Cruisers Comparison - Seven Sport-Cruiser Motorcycles| first1= Art| last1= Friedman| first2= Andrew| last2= Trevitt| first3= Andrew| last3= Cherney| first4= Jamie| last4= Elvidge| first5= Evans| last5= Brasfield|date=April 2000| work= Motorcycle Cruiser| publisher= Source Interlink Media| at= "Take a Spin" section, paragraph 4| access-date= 2010-09-10|archive-url=https://web.archive.org/web/20100502180324/http://www.motorcyclecruiser.com/roadtests/sport_cruisers_comparison/index.html |archive-date=2010-05-02|url-status=live| quote= Though the Valkyrie also has a longitudinal crankshaft, this torque reaction has been eliminated by making some of the components, such as the alternator, spin the opposite direction of the engine.}}</ref><ref name="TamingTheBeast">{{cite web| url = http://www.breganzane.com/vm/history/v6/page3.html| title= Developing the V6 - Taming The Beast| first= Stephen | last= Battisson | year= 1997| work= The Laverda V6| publisher= Stephen Battisson| page= 3| access-date= 2010-09-10| archive-url =https://web.archive.org/web/20110708092245/http://www.breganzane.com/vm/history/v6/page3.html | archive-date =2011-07-08 | url-status = dead| quote= By arranging the rest of the engine internals to rotate in the opposite direction to the crankshaft their forces are cancelled out without having to resort to the weight, complexity and friction associated with two crankshafts.}}</ref>

Longitudinal V-twin engines have been used by the [[Honda CX series]] and several [[Moto Guzzi]] motorcycles.

<gallery mode="packed" heights="200px">
File:Honda Longitudinal V-twin.JPG |1978–1983 [[Honda CX series|Honda GL500 Silver wing]] {{nobr|80° V-twin}}
File:Moto Guzzi V-twin.JPG |2000 [[Moto Guzzi#2000–2004 – Aprilia years|Moto Guzzi Jackal]] {{nobr|90° V-twin}}
</gallery>
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