What is the main verb in this sentence you probably should have biked a less difficult route.?

The main verb in the sentence "You probably should have biked a less difficult route" is "should have biked".

Here's why:

* "Should have biked" is a modal auxiliary verb (should) followed by the past participle of the verb "bike" (biked). This combination creates a past perfect modal verb form.

* "Should" is a helping verb that modifies the main verb "biked".

* "Have" is another helping verb that assists "should" in forming the past perfect tense.

The rest of the sentence ("a less difficult route") acts as the object of the verb.