The manual recommends that the plastic expansion tanks is drained (by removing) and refilling separately if I recall. That looks tricky because of access but to be honest I don't plan to do mine just yet so I have not looked into this. I plan to do mine in a couple of years. Regarding air being trapped, that is not a normal occurrence on bikes. After re-filling the bike at the main fill cap, then revving the engine a few times with the cap off usually does the trick.Whats involved in replacing coolant? Drain and refill and thats it? Its pretty complicated on my truck because of air bubbles being trapped.