Welcome from South Florida. I am completely new to the forum world and owning a 4x4 for that matter. Idk if I am even posting this thread rigjht but if I am I could really use some help.
I just recently purchased a 2007 650i brute force. It' is snorkeled with custom tires, exhaust, clutch, belt, and other upgrades. I just took it out to Mudjams and the bike was an animal through the mud. When I was in the mud I went to put the bike into 4 wheel drive but I wasn't moving. I just found out that to operate 4 wheel drive you need to be moving from what I was told. As soon as I went in to 4 wheel drive the bike started making like a knocking noise which seem to be echoing from my right snorkel. Now im not mechanically inclined by any means so I don't even know where to begin. Also it seemed to have like a grayish smoke coming from the snorkel as well. Now the bike seems to be bogging out when I give it gas. Any ideas or suggestions?