Rules for verbs are: 1) In main clauses, the conjugated verb is in the second position (counting grammatical relevant parts of the sentence). It is NEVER in first position. 2) In questions, and in questions only, the conjugated verb is in the first position. 3) In subordinate clauses, the conjugated verb is in the last position. One can recognize subordinate clauses by the conjunction, such as "weil", "dass", "obwohl", etc. There are also conjunctions for main clauses, like "denn" and "aber". 1) "Ich kann Zeitung lesen.". 2) "Kann ich Zeitung lesen?" 3) "..., weil ich Zeitung lesen kann", "..., obwohl ich Zeitung lesen kann". But: "..., denn ich kann Zeitung lesen", "..., aber ich kann Zeitung lesen". The same works for any other word, it's not a condition related to "kann". The point is that in a construction "können + infinitive", "können" is the verb that gets conjugated. If you change the sentence so that a different verb is conjugated, then the rules apply to this verb. 1) "Ich soll einen Aufsatz schreiben." 2) "Soll ich einen Aufsatz schreiben?" 3) "..., weil ich einen Aufsatz schreiben soll." 1) "Ich lese Zeitung." 2) "Lese ich Zeitung?" 3) "..., weil ich Zeitung lese." For every example, it's the same set of rules.

The rule is simple: In a subordinate clause, the main verb goes at the end of the sentence. This is VERY elementary grammar. Are you really studying?

I see ,so your question is not about 'weil'. 'kann' is a verb KÖNNEN. As a rule in subordinate clauses ( the sentences coming after the comma) the verb will always stand at the END. If you say ,you usually see the auxiliary verb (Modalverb) at the beginning ,that is because you are talking about its position in the main clause of the sentence. 'Ich kann Deutsch sprechen.' 'Er kann das Buch nicht finden.' An auxiliary verb is by definition assisting another verb in the sentence, so when 'kann' is used, there will be another verb to end the sentence with and even normal verbs will stand as part of the sentence's predicate ( verb + objective) at the beginning of the sentence after the Subject. (Subjekt + Predikat auf Deutsch). I think you are at an early stage of learning German,that is why you are not so familiar with NEBENSÄTZE and the position of the verbs in general at the end of it ( inclusive the verb 'kann' in your question). We can discuss that further ,if you don't get it yet :)

here what i want to know is when starting with weil, we put "kann" or word like that in the end. That is not a usual condition I see for "kann". I often see "kann" is put in the front of sentence. So there may be a rule there, but I don't know what exactly that is.

It is a German 'question' by the way ;)