Backfire is unfortunately normal. Adjusting the idle mixture jet will help with that, as may fiddling with the jet needle spacer.
Removing the tank is somewhat easy. Remove the seat (two bolts with 10mm heads toward the back), then remove the two bolts for the seat hold-down clip in front. This also bolts down the tank. Be sure the fuel petcock in in "ON"; remove the two hoses from the petcock. Remove the speedometer cable from the transmission and keep track of where the little black grease seal washer rolls. Lift the back end of the tank as you pull it backwards and swear mightily as the fuel petcock snags under the frame and you don't get the tank off. Wiggle the tank just right and it'll pull up & back. Disconnect the electrical connector under the tank that feeds the lights in the instrument cluster.
Buy HiProFiltro brand oil filters from any non-Suzuki motorcycle shop, about $5 each. My choice for oil is any synthetic 5W-40 diesel engine oil; I prefer Mobil Delvac 1.
The white spacer is accessible with the tank off. Remove the four screws holding down the top of the carburetor diaphragm housing, note the tab on the diaphragm fitting into a matching groove in the top, remove the diaphragm and all the bits attached. Note exactly how the little brass plate with two tiny screws is situated down inside the black cylinder. The white spacer is inside this, along with a spring that will make things interesting. I found that four 3mm washers gave me the needle lift that works very well for me, about 2mm of thickness. If your #4 washers work for both ID and OD, OK. Put everything back exactly like you found it with the diaphragm edge in the groove and the big spring in the middle of the cap.
Yep, if it ain't broke, don't fix it.
Put one of these R1106 magnets on the top of your oil filter to catch the iron particles that are too small to be trapped in the filter. This will help reduce engine wear.
http://www.supermagnetman.net/product_info.php?cPath=41&products_id=404I like the addition of a fork brace to smooth out the front end. Either the $92
Tkat Special or the prettier $165
SuperBrace.
Build yourself a lift out of two 2x8s nailed together
http://www.nightrider.com/biketech/bikelift.htm