Mangahelpers doesn't host raws anymore, but google is your friend.
I would reccomend irc-distro for hq raws. #irc-distro on irchighway, and theres always lq share raws from numerous websites (for example rawpiece.com). But if your looking for raws to practice cleaning definitely use hq raws.
Of what? Please do specify, since there's actually no one website that host every single raws in the universe. So, either specify the manga series, or at least the magazines, or yeah, google for them yourself. .-.
I was gonna ask the same question, but you beat me to it! Lol thanks for asking and thx for the answers...
i found a new RAW Manga site and it renews fast.hope it will help you!
there is RAW many places try to Google it or you can try at Raw Scans