Secure the chain by maintaining upward tension on it with tie wraps or mechanics wire. It doesn't need to be pulled/secured from the absolute top. Tie wraps could go on the chain sides at the level of the top of the head around a long screwdriver across the cavity opening. If the links around the cam sprocket aren't pulled tight that is ok. The goal is to not let the chain get lowered off of the lower sprockets that you cannot see or reach. You'd be amazed how a slight drop in the chain can cause it to fold on itself, slide into a hole and get bound up.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer