| CPC F02M 25/0836 (2013.01) [F02F 1/40 (2013.01); F02F 1/4285 (2013.01)] | 20 Claims |

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1. An off-road vehicle comprising:
a frame;
a pair of front wheels;
a pair of rear wheels;
a controller;
a suspension system, comprising a front suspension and a rear suspension, the front wheels being connected to the frame by the front suspension, and the rear wheels being connected to the frame by the rear suspension;
an engine supported on the frame, at least one of the front or rear wheels being rotationally driven by the engine, the engine being equipped with a combustion chamber, the engine comprising a cylinder block and a cylinder head connected to the cylinder block, the cylinder head being equipped with air intake passage and an exhaust passage;
a fuel supply system for supplying fuel to the engine;
an exhaust system comprising an exhaust conduit and a muffler communicating with the exhaust conduit, the exhaust conduit communicating with the exhaust passage in the cylinder head;
an intake system through which air is fed into the air intake passage; and
a supplementary air supply passage for mixing air into the exhaust gas discharged from the combustion chamber, wherein air flow through the supplementary air supply passage is electronically controlled by the controller controlling a valve and/or an air pump.
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