Thinking about getting a 400.

[SS Adrenaline]

Talked to this guy yesterday. He said the currently, the bike only idles when on the choke.  What could cause that?
http://seattle.craigslist.org/est/mcy/3012161491.html

I am thinking about going to check it out and measure the compression. What are gsf400's good compression?

Anything else I need to pay a particular attention to?

What this could mean is the the mains are plugged or partially plugged and not getting enough gas.  When you hit the throttle this lets more air through the carb but no more fuel through the jets, causing the bike to run lean to the point of stalling.  Another possibility is that there could be an ajustment somewhere.  I would have to look into a manual.  Can you give any more information?  What do the plugs look like?

[taijinian]

I haven't seen the bike yet. However, the ad says that carbs were serviced recently, so it would be surprising that the jets could be clogged.

[SS Adrenaline]

I haven't seen the bike yet. However, the ad says that carbs were serviced recently, so it would be surprising that the jets could be clogged.

Yes it would be surprising however there are those that can make mistakes upon rebuilding, even by a dealship.  The floats might need adjusting and werent when they were serviced.  You might want to ask them if it was running ok befor the cleaning.  Its just a thought.