Timing belt

Hi, I have a sound coming from my timing belt and i think it's because it's to tight, is it possible to get the top cover off without taking the bottom pulley off?

also quick question, when it says tighten 20nm then by a further 86° ± 6° For example what's the ± 6° bit?
 
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It means within 6 degrees. It's kind of a bit of leeway. So anywhere between 80 and 92 degrees.

taking the top cover off isn't going to help, I don't think you'll be able to tell if the belts too tight that easily. What noise is it making?