Hi guy's

The timing belt failed on my 52 plate st170.
So I bought this timing tool http://www.ebay.co.uk/itm/281921495649 . but the bar that slots into the end of the cams won't fit in.
Every guide I can find the tool just slots In the grooves, but the cams sit just below the casing so the tool won't slide in

Any advice on how to make sure one cam isn't 180° out would be great too

Thanks