| 摘要 |
A cam holder includes a second air passage. A lower knock pin is positioned in the second air passage and service to position the cam holder on a cylinder head and to connect the second air passage to a first air passage formed in the cylinder head. The second air passage is bent and can be formed by machining from two directions into in the cam holder. The lower knock pin is press-fitted in a first groove around a perimeter of a lower opening of the second air passage. A second groove can be formed around the first groove to accommodate an o-ring. An upper knock pin is press-fitted in a third groove around a perimeter of an upper opening of the second air passage. The upper knock pin serves to position the cam holder on a cylinder head cover and to connect the second air passage to a third air passage formed in the cylinder head cover. The first, second and third air passages form a secondary air supply passage to supply cleaned air to an exhaust port in the cylinder head and thus improve the emissions of the exhaust system.
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