Well you have to consider the ticking noise may be totally separate from the loss of power.
What did the owner say about it? Did the ticking start at the same time as the power loss? Did he have it looked at? What makes him say it lost power?
I'm at a loss thinking the Bike just started ticking and lost power and then the owner just decided to sell it as is, without attempting to find out what the problem is.
What if it's just bad gas?
How long has he owned the VMax?
Has he ever done any work on it? ie: tune up, oil changes, had the valve covers off, or carbs off?
What mods has he done, if any?
What do the spark plugs look like?
What some people would call ticking, I find that it is sometimes normal engine sounds. The first time I rode my Max, I thought to myself, "man, is this supposed to sound this way?" The answer was Yes. It's normal. Nothing sounds weird to me any more, but some times people ask me why does it tick like that.
Loss of power could come from many things. Has the owner had the carbs adjusted by someone who knows how to adjust Quad Carbs properly with a sync tool? Not some Harley buddy of his, who just says he can do it by ear.
Has he had the fuel mixture adjusted? Have the brass caps on the fuel mixture screws been drilled out and replaced with rubber plugs? This will tell you if someone has played with the fuel mixture.
Maybe he was tinkering around doing some mod to it and accidentally unplug the vboost servo motor?
I know being how you are not the owner, some of these things you will not know. But you may want to write them down and ask the owner.
I'm not by any means an expert at troubleshooting the VMax. But I have learned a lot having owned one for 2 years now. What I am good at though is solving problems. And in order for the gurus in here to help you better, these are some of the questions that need to be answered in order for you to get the most accurate diagnosis.
I'm not trying to be a butt head, I'm just trying to help in the best way I can.
Good Luck!
I'm sure with more info a lot of the guys in here will be able to help you get everything sorted out.