why were the french at first reluctant to sign an alliance with the colonies

Some French leaders were reluctant to aid the colonists because of the cost and uncertainty of the outcome. Also France's navy was weak.

http://en.wikipedia.org/wiki/France_in_the_American_Revolutionary_War

because u are stupid

The French were initially reluctant to sign an alliance with the colonies during the American Revolutionary War due to a few reasons:

1. Risk of Failure: The American colonies were engaged in a rebellion against their British colonial masters, and at the time, the outcome of the war was uncertain. France, being a major European power, was cautious about aligning with a group that might ultimately face defeat. They did not want to risk damaging their reputation by taking on such a risky venture.

2. Financial Considerations: France had previously experienced significant financial strain from various conflicts, including the Seven Years' War. Getting involved in another war would require substantial financial resources, which France was not initially prepared to commit to.

3. Diplomatic Implications: France had recently signed a treaty with Britain in 1763, marking the end of the Seven Years' War. They feared that joining the American colonists against their British rulers could potentially strain their relationship with Britain and even result in retaliation from the British Empire.

4. Hesitation about Revolution: France had its own internal issues at the time, with a growing discontent among its own population against the monarchy. They were cautious about supporting a revolutionary movement, as it could potentially inspire similar sentiments among the French people, stirring up further unrest.

Despite these initial reservations, the French eventually decided to sign an alliance with the American colonies in 1778. This decision was influenced by factors such as the successful American military campaign and the belief that supporting the colonies would weaken their long-time rival, Britain. Additionally, the Battle of Saratoga in 1777, which resulted in a decisive American victory, convinced the French that the Americans had a substantial chance of winning the war, making it a more attractive proposition to support them.