123 Crisp Dr, Americus, GA. 31719

Cam Degree 101

Motorcycle Camshaft Installation Instructions

1. Install cams using stock timing marks.

2. Locate TDC on the degree wheel using a dial indicator or a positive stop.

3. To find intake lobe center, rotate engine until you have found maximum lift using a dial indicator on the lifter. Zero indicator with cam at maximum lift. Rotate engine in reverse direction until indicator drops 0.040". Rotate engine in normal direction until you are 0.020" below maximum lift. Mark or note degree wheel location. Rotate engine in normal direction, going through maximum lift and until you are 0.020" below that point. Mark or note degree wheel location. The intake lobe center is located at the point mid-way between these two readings. The intake lobe centerline is determined by calculating the number of degrees from your TDC reading to your lobe center reading.

4. Repeat step 4 to locate the exhaust centerline.

5. You must check the following clearances:
a. Valve-to-piston
b. Valve-to-valve
c. Coil-to-coil
d. Retainer-to-guide

6. Generally, the effect of moving lobe centers is as follows:
Advancing the intake and retarding the exhaust (“closing up the centers”) increases overlap and should move the power up in the RPM range, usually at the sacrifice of bottom end power. The result would be lower numerical values on both intake and exhaust lobe centers.
Retarding the intake and advancing the exhaust (“spreading the centers”) decreases overlap and should result in a wider power band at the sacrifice of some top end power. This condition would be indicated by higher numerical values on both intake and exhaust lobe centers. By moving only one cam the results are less predictable, but usually it is the intake that is moved to change power characteristics since small changes here seem to have a greater effect. With twin cam engines we have the luxury of moving the cams independently.

7. Over torqued and sloppy sprocket slotting can result in flange breakage.


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