First there are two errors in your sentence:
Ich finde Sport nicht so gut, weil er anstrengend ist und ich faul bin!
In German "I" is "ich". The word "er" or "es" is a reference to "Sport" and must be in the gender of "der Sport" (male). So you have to use "er" (male) instead of "es" (neutrum).
The word "und" is a conjuction und combines two parts of a sentence. You can also write the complete sentence:
Ich finde Sport nicht so gut, weil er anstrengend ist und weil ich faul bin!
Here you see, that the leading "weil" forces "bin" to be at the end of the sentence (that's the reason why your first sentence is wrong). In German you can leave out some words which are only repeated like the second "weil", but the position of "bin" is not changed. So you get the right sentence:
Ich finde Sport nicht so gut, weil er anstrengend ist und ich faul bin!
If you use a sentence like:
Ich finde Sport nicht so gut, weil er anstrengend und schlumpfig ist.
this sentence can also be completed to:
Ich finde Sport nicht so gut, weil er anstrengend ist und weil er schlumpfig ist.
Here you have the same helping verb (Hilfsverb) "ist" (thats the difference to your sentence) and the same subject "er". The double words "ist", "weil" and "er" can be leaved out.
Remark: write instead "schlumpfig" everything that fits and what you want, it is absolutly not important for the construction of the sentence. The only important thing is that there are two "ist" in the German sentence to show how you can leave one out. If you do not know "schlumpfig" have a look on german Wikipedia.
of the answers
. And you didn't not correct the question, but rolled back the correction, to tell the truth. So if you would please join the meta discussion, and explain, why you think that this is the preferred behaviour.