If you can only do 1 video a week, stick with that and post at the same time on the same day each week. If you are able to record more videos, don't adjust your schedule, just bank them which will allow a buffer for if you can't get out one week.
Work on your tags and descriptions so that YouTube can work out who to suggest your videos to.
Decent thumbnails, video titles and wording on thumbnails to draw attention to them over other people's vids.
Marketing, you have to do some donkey work to grow an audience, social media is your friend here, and in my book is a must to use Facebook.
Scratching backs and shoutouts, your main audience when growing your channel will be other motovloggers, so network, take an interest in their content, they may then take a look at your channel. Don't ask them to on their vids though.
I can't remember from your vids that I have watched so far if you ask folk watching to "like", "comment" and "subscribe"? It sounds cringy, but it seems to work. Don't do it right at the beginning though as anyone watching will have forgotten by the end.
Assuming you have gotten your current subs without paying for them or doing Sub4Sub, then you must be doing something right.