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Old 11-03-2010, 09:02 AM   #24
Beastly Adventurer
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Joined: Jun 2004
Location: Nor Ca.
Oddometer: 5,000
Originally Posted by gapek
Thanks for the info, I'm doing the valve adjustments right now and your posts are like a Bible to me ;)

I noticed one thing, in the BMW DVD service manual is stated that to measure TDC on cylinder #2, you have to rotate 360 degrees… it does not make sense, because after full 360 rotation you’re back in TCD #1 position. I did like you have posted: 180 degree rotation, IN and EX marks and in the same level but pointing in opposite directions – front and rear of the bike.
I’ll post some more info when job will be finished.
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.
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