No they are quite tight when you first install them, there's nothing you can do wrong in this respect, unless you have overtightened the left hand crank arm cover. The rating is for 4Nm but this varies with each crank. You need to feel when the crank is getting harder to turn. That's when you should back the cap off a bit. Don't worry about it falling off though, the two pinch bolts will secure it. The cap is merely a bearing adjuster. To give you an example, my Ultegra cranks turn 2 or 3 revolutions max. with well over two thousand miles on them.
Hope this helps.
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Matt
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