Besides the big four, are there any other publicly held companies within the MX or dirt bike world?

Polaris (PII - NYSE). They have an equity postion in KTM (I think about 50%) with an option to buy them out in the next couple years. KTM has a very reasonable stock price and good growth over past few years. PII looks cheap also. A couple highly rated mutual funds have big positions in PII: Muhlenkamp and Liberty Acorn. I have seen PII recommended in a few places, it has gone down some this year, possibly a good buy.