Motorcycle Repair: Bike wont start and engine is not running steady, suzuki dr200, motorcycle technician

Question
Hi Mike

Thank you for your time and help.
My name is Isabelle.  I just got my second bike, I am the 3rd owner.  It is a Suzuki DR200 SE with just over 600 miles.  Year is 2000.  The bike has been seating still quite a lot as the 2 previous owners did not ride much (obviously! :) )
I got the bike just two weeks ago.  I have had problem starting the bike.  The few first time it did start really fine, and then, it did not.  Also, the engine runs sometime high and then low, so it is not steady.  I replaced the battery and that did not solved the problem.  A good friend of mine that ownes 17 bikes checked it out and said the start plug and the air filter are clean and in good working condition.  Do you have any idea what can cause these problem, first problem being that the bike does not start (it will when jump started) and why is the engine not running steady , even after being jumped start.  (sorry, English is not my first language, so I do not have all the words needed to describe the situation.)  Could it be the carburator?  Could it be that the engine, because of sitting too long got some debri in it?  I just ordered the repair manual and will bring it, with the bike, to a friend who is a motorcycle technician and I wanted to have your idea and suggestions.
Thank you so much for your help.  I cannot wait to ride.  
thank you again
let me know if you need any more detail that could help you answer the question
Isabelle
Venice, CA

Answer
Hi Isabelle,

The carburetor will need to be cleaned. Fuel changes chemically from a liquid, to a gel, and eventually to a corrosive powder. The early stages of this process is know as "varnishing" or "gumming." This is very common as owners bring their MC's out of winter storage each Spring.

The pilot jets and pilot circuits usually become obstructed. The enrichment circuit (choke) shares passageways with the piolt circuit. If the engine runs on choke only, this indicates the pilot circuit is obstructed.

It may need a new battery or charging to restore the battery to good working condition.

Change the engine oil and filter. Oil dosen't age very well.

Contact me as necessary for asistance. I have many files on MC repair. I need an email address to return files.

Respectfully,
Mark Shively