As above, there are ways if you know the timing is correct with current belt.
It would involve something like below .... please note, i have never done this, and don't recommend doing so !!!
You would need to acurately mark the position of the two cam pulleys relative to each other (and the head) once the mark on the crank pulley is lined up, and piston no.1 is TDC.
You would also need to mark the belt and relative position on each of the 3 pulleys.
You then transfer these marks to the new belt, making sure the number of teeth between each mark is the same as old belt.
Then comes the hard bit, making sure the cams don't move when you remove the belts, which is what the locks do !
If you have enough hands, you could hold the cams in position as you place the belt on and get some tension into it.
If ALL the marks made are lined up, then the timing should be correct.
But as above, I WOULD NOT recommend doing it like this.
I've never used this process.
for the amount of money they cost, you'd be better off buying a set of locks, or borrowing some.
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