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YFZ450 Exhaust Cam Retard
INTENDED: YFZ450 | PERFORMED ON: YFZ450 | DIFFICULTY: 7/10
INTRO: Retarding the exhaust cam sprocket one tooth on the timing chain, affectionately known as the "cam mod", has proven to boost power in the mid to upper range of the powerband on the YFZ450. This free modification can make starting easier too, especially if you've added a kickstarter. It's a fairly simple procedure which should only take about an hour. We recommend an increase in pilot jet size along with this (we used a 48-pilot), but as always, jet accordingly to your needs.
STEP ONE: You'll first need to remove your gas tank. We'll assume you can do this without instructions. Once removed, you should clean the top of the engine and the above frame rails, along with all hoses and wires thoroughly. After that, go ahead and remove the two hoses attached to the top of the valve cover, without losing the clamps. Also remove the spark plug cap from the spark plug.
STEP TWO: Now you can remove the two allen-head bolts located in the top of the valve cover, as seen in the photo. When both are removed, you can pull the valve cover off and set the rubber gasket back in the cover itself, as shown here. Now remove your spark plug with a spark plug socket.
STEP THREE: Remove the two caps from the flywheel cover shown here, with a large flat-head screwdriver or something similar. Using a rachet with the correct size socket on the flywheel nut, turn the motor over slowly (make sure transmission is in neutral) in a counter-clockwise direction, until TDC (top dead center) is achieved. Do this by looking through the window on the flywheel cover until you see the timing mark on the flywheel itself. This can be hard to locate, so look at your exhaust and intake cam sprockets for verification. The marks on both sprockets should be in place like they are in this photo.
STEP FOUR: It's time to remove the automatic timing chain tensioner, which is located on the backside of the cylinder. First loosen the 10mm center bolt, but do not remove. Then, remove the two 8mm bolts that hold it in place. This can be troublesome, as the bolt farther from you can be difficult to get to. Once you have both bolts removed, pull the entire assembly out of the motor. If the gasket is damaged, replace it.
STEP FIVE: Using a magic marker, make a mark right below the cam sprocket tooth which is right beside the factory "B" marked tooth on the exhaust cam sprocket. Also make a mark on the timing chain itself, corresponding with the mark you made on the sprocket. Do the same with the intake cam sprocket. It doesn't matter which sprocket tooth you mark on this one, just as long as it's easily visibile, like here.
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TECH
