[shambhalove.]

1) Don't top a Maple, or any tree for that matter, ever.

2) Don't prune it in spring, Maples bleed a lot and pruning at the wrong time of year can kill an already weakened tree. Late summer (after it has leafed out fully) or later winter is best.

Honestly its not looking so good, hard to tell but did the top die back already? Personally I would make sure it gets lots of food and water this summer and then think about pruning at the right time and when the tree will handle it better.

 

[shambhalove.]

Topping is one of the worst things you can to do any tree and its frowned upon in the arborist community. But its important to understand what topping is, there are ways to reduce a trees height without topping it...pollarding(like on citrus), drop crotching, redirects, ect. But dont just take my word for it!

http://www.treesaregood.com/treecare/topping.aspx