rear bumpers?

I have seen rear bumpers for other quads, but have not seen one for a 400EX. I want something to protect my swingarm & rear brake caliper when I stop short & the kids aren't paying attention. They slam into me quita a bit..... :rolleyes:

where can I get one & what should I expect to pay?

are there any disadvantages to having one, such as more difficult chain adjustment?

I don't know for sure, but DG may have one. Like you mentioned, it does make it harder to adjust the chain. My friend has one on his 300EX, and it seems as if it will do you more good than it does him(the little ones and all;) ).