When my question gets down voted, I always ask why my question got down-voted in the question's comments. I don't always receive a response and this leaves me confused. If I do not get a reason behind the down vote, can I just post a question on the meta site and ask for help in improving the question?
Technically you can.
I prefer you, and many others, don't. Or at least not at the first downvote.
I always ask why my question got down-voted in the question's comments.
Don't do that. That is not where comments are for. It is noise. I've flagged the two comments you left under the same question. Use comments only to clarify the post.
A vote indicates usefulness for future visitors. It is always a judgement call by the voter and it is therefore pretty useless to have each and every vote explained because judgement calls don't lend themselves to be rule-lawyered. Besides usefulness, clarity and how well the question is researched are other criteria questions better abide to.
A voter is most likely to never return to your question again. If you pick up four comments within eight minutes of posting and you need to edit your question due to that, you have the explanation of the downvotes. You were too quick with posting and should have given it another hour or so. There is plenty of time to prepare a good question, but only so little time to fix it once it is live.
One of the mistakes many users that ask about downvotes make is: Asking for things they are already told. If there are comments under a question that point out an issue or suggest researching topics you have already got the feedback you're asking for. Posting on Meta will then be seen as: I've happily ignored all guidance already provided to me, but instead I continue whining about a downvote. The meta crowd sees no reason to go gentle when they suspect this reason from the OP.
In the end, if you still insist on coming to Meta, you still have to do the same research, and the same due diligence as if you post on Meta. It is worth keeping in mind that the Meta regulars optimize for the knowledge base towards the future. They have no emotional bond with your question, and they honestly don't care. Only if they see possible value for generations to come might be lost, they will guide OP's and rectify mishaps. The onus is on you to explain where the value is in a question that received a downvote. If Meta doesn't get convinced the Meta effect might backfire a bit.
TL;DR; Can you ask on Meta for help in improving a question?
You can, but only if it is 100% clear that a question has value, all possible options to improve have been exhausted, all comments have been addressed and the Help and question checklist are applied. I have also written this guidance for a slightly different use case, but you might find that advice useful as well.