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Old 11-03-2010, 09:16 AM   #25
Camel ADV OP
aka Oso Blanco
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Joined: Mar 2009
Location: Cowtown
Oddometer: 1,500
Originally Posted by itsatdm
I am not sure, I understand what you did or you understand what the manual meant to say. The cams move at half the speed/distance of the crank. 1 360 degree rotation of the crank puts the valves TDC on the compression stroke on #2, but the cams have only moved 180 degrees.

In a 360 degree twin like the 800, the pistons rise and fall together, but fire alternately. It is a 4 stroke so it requires 2 revolutions of the crank for the cylinders to complete the cycle, ie 720 degrees. On the timing marks on #1 for both cam and crank, you are on TDC for the compression stroke, cam lobes fore and aft. Turn the crank 360 degrees, ditto for #2. Another complete revolution of the crank, back to #1.

Sounds like you did it right, based on the location of the cams fore and aft, when you took the measurements. The marks on the cam faced away and not inward.

I'll go back and clarify that point. Because you (or I did anyway) rotate the motor with rear wheel, it's tough to watch the timing mark on the crank and turn the tire at the same time so I was watching the cams, which as itsatdm said rotate 1/2 as much as the crank. The BMW manual is correct stating that the crank should rotate 360 degrees for the #2 cylinder check.
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