2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 51Get this manual
TECHNICAL FEATURES
HOT START SYSTEM (TRX450R only)
The hot start system creates lean airfuel mixture that enables hot engine to be started easilyWhen the hot-start lever (located on the left side of the handlebar) is pushed away from the rider, the hot start valve in the carburetor opens, supplying air to the main bore through the hot start air passageThis extra air blends with the airfuel mixture from the slow circuit resulting in lean conditionHOT START VALVE
HOT START AIR PASSAGE