I would not use that sentence structure, regardless of grammar.

I would use:

Do you know the time when the class starts?

or:

Do you know the time when the bus leaves?

I would not use that sentence structure, regardless of grammar.

I would use:

Do you know the time when the class starts?

or:

Do you know the time when the bus leaves?

Even better:

When does the class start?

or:

When does the bus leave?