when u line up the pulleys when putting on the belt make sure it hasnt moved any. sometimes itll move oh so slightly and cause it to be off. Clamp the belt to a cam so it doesnt move when its perfectly lined up and try that.
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1990 Honda Civic DX Hatchback - SOLD
2006 Scion tC - Traded
2013 Fiat 500 Abarth - Current DD