I just bought a suzuki fa50 that was in storage for 2 years. I changed the spark plug, drained the old oil, but just put new gas on top of the old gas. Sometimes it runs fine. But about every other day it bogs and dies when it warms up. Then it wont start for a while. Could it be the gas? How long should I let it warm up before I drive it? There is usually a little white smoke from the exhaust for a bout 5 minutes when I start it. I usually wait til its clear to drive it. Thanks for any help.