1979 GL1000 Timing belts

[Benjiiboy]

Hi, completely new to the goldwing, and this sight, not new to turning wrenches. As I have a shop full of bikes, the 1979 Goldwing, an 88 750c, and a few others.

But as I was doing the timings belts on the 79', I get everything all lined up, but when try to get the belt tensioned up it pulls it out of time. Is there something I'm missing? Like too add, when looking at the front of the motor, the right belt was already brand new, this is the left side, again when looking from the front.

Thank you Ben!