I think that if you plan on being in the biz for a long time, then now is the time to get the name straight, and not another 5 years down the road.
I agree that the J J W is kinda dull and these types of names are overused. Think long and hard about it because once you change it, you will likely never be able to do it again without detrimental effects. You have the creativity to come up with something good, and make it something that you can apply to both markets. Don't sound too corporate or too MX, find a good common ground and use a different logo for each market. Something that the MX guys will like to show off on their bike, and another logo to use with the sign biz with a bit more of a professional look. I WOULDN'T use the word FLAME in your name at all......