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[[Image:Yfzdyno7.JPG|400px|thumb|right|Dyno run of stock YFZ450 (blue) vs a YFZ450 with a slip-on, cam mod, rejetted, and airbox lid removed (red)]]The cam mod, in regards to the [[YFZ450]] [[engine]], refers to retarding the timing of the exahuast [[camshaft|cam]] by one tooth. What this does is brings the YFZ's timing to the same as that found in the YZ450F dirtbike's engine. Contrary to what [[Yamaha]] might say about this mod, it will not ruin your engine provided the mod is done correctly.

== Performance ==
The majority of the effects of the cam mod can be felt in the mid to upper RPM range.

The idea behind the retardation of the exhaust cam has to do with the duration of maximum compression of the engine. Since the exhaust gas is not able to leave the cylinder as early, its expanding pressure is applied to the piston longer. This force is thus pushing downward on the piston a further distance resulting in an increase in work when compared to the same situation with stock timing. An increase in work done on this piston is translated to more torque on the crankshaft and thus more horsepower.

== Tutorial ==
*Make sure the quad is clean of dirt, sand, mud, etc.
*Remove gas tank cover and side panel plastics.
*Turn off gas and disconnect the fuel line from the petcock assembly on the gas tank.
[[Image:Cammod01.JPG|600px|thumb|center|Disconnecting fuel line]]
*Remove gas tank.
[[Image:Cammod02.JPG|600px|thumb|center|Gas tank removed]]
*Remove plastic gas tank shield.
*Disconnect ignition coil and both breather hoses from head cover.
[[Image:Cammod03.JPG|600px|thumb|center|Disconnecting coil and hoses]]
*Remove spark plug.
[[Image:Cammod04.JPG|600px|thumb|center|Removing spark plug]]
*Remove both head cover bolts.
[[Image:Cammod05.JPG|600px|thumb|center|Head cover bolts]]
*Remove head cover.
[[Image:Cammod06.JPG|600px|thumb|center|Head cover removed]]
*Remove both timing plugs on left crankcase cover.
[[Image:Cammod07.JPG|600px|thumb|center|Timing plugs removed]]
*Remove chain tensioner cap bolt.
[[Image:Cammod08.JPG|600px|thumb|center|Removing chain tensioner cap bolt]]
*Using a small flat head screwdriver, retract the chain tensioner by turning clockwise until it stops rotating.
[[Image:Cammod09.JPG|600px|thumb|center|Retracting chain tensioner]]
*Rotate crank to [[top dead center]].
[[Image:Cammod10.JPG|600px|thumb|center|Rotating crank]]
[[Image:Cammod11.JPG|600px|thumb|center|Top dead center can be found by aligning the mark at the top of the upper timing plug hole with the single mark on the flywheel]]
*Remove camshaft cap bolts in stages in a criss-crossing pattern.
[[Image:Cammod12.JPG|600px|thumb|center|Order in which to remove camshaft cap bolts]]
*Remove both camshaft caps. Be careful not to lose the clips underneath the caps.
[[Image:Cammod13.JPG|600px|thumb|center|Camshaft cap removed with clip on camshaft]]
[[Image:Cammod14.JPG|600px|thumb|center|Camshaft clip]]
[[Image:Cammod15.JPG|600px|thumb|center|Both camshaft caps and clips removed]]
*Take note that at top dead center before the cam mod, outer marks on camshafts both align with the top of the head.
[[Image:Cammod16.JPG|600px|thumb|center|Both camshaft marks in line with top of head]]
*Retard the exhaust camshaft clockwise one tooth. This is done by wiggling the camshaft out to where there is enough slack in the chain for the teeth to retard one tooth.
[[Image:Cammod17.JPG|600px|thumb|center|Retarding the exhaust camshaft]]
*After the rotation of the exhaust camshaft, there should be a difference in the alignment of the marks on the camshafts. This will tell you if the mod has been done correctly.
[[Image:Cammod18.JPG|600px|thumb|center|While the mark on the intake camshaft is still in line with the top of the head, the mark on the exhaust side is one tooth up]]
*Replace the camshaft clips and caps back over the camshafts. Remember to be careful not to lose the clips.
*In the same pattern as before, screw in the camshaft cap bolts in stages. (Torque: 10 Nm, 7.2 ft·lbs)
*Release the chain tensioner by beginning to screw it counter-clockwise and then letting it freely turn itself until it stops.
*Rotate the crank a few times to ensure that everything is still rotating freely.
*Replace chain tensioner cap bolt. (Torque: 7 Nm, 5.1 ft·lbs)
*Replace head cover and secure with head cover bolts. (Torque: 10 Nm, 7.2 ft·lbs)
*Replace spark plug. (Torque: 13 Nm, 9.4 ft·lbs)
*Reconnect ignition coil and both head cover breather hoses.
*Replace timing plugs.
*Replace gas tank.
*Reconnect fuel line to petcock on gas tank.
*Replace gas tank cover and side panel plastics.
Once the mod has been fully completed, a [[rejet]] is suggested.

== External Links ==
*Step-by-step [http://yfz450.theatvchannel.com/invision/index.php?showtopic=59800 Cam mod tutorial] on YFZCentral written by Terse
*Video series of the mod done by Dogriders
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z01.wmv Removing plastics]
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z02.wmv Removing cam tower]
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z03.wmv Setting top dead center]
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z04.wmv Marking the cams]
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z06.wmv Removing chain tensioner]
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z08.wmv Removing cam journals]
**[http://www.allthingsmoto.com/forums/yfz450_videos/cam_mod/z09.wmv Cam mod]