20 degrees initial seems a little high. Advanced timing at idle will increase the unburned hydrocarbons or fuel (HC) in the exhaust tremendously. Try backing the timing down to about 12 degrees and see if the smell improves. Throttle response might not be as crisp though. It's a common practice for manufacturers to retard ignition timing at start up. I've seen some run as much as 5 degrees retard for the first 30 - 60 seconds of operation. The engine doesn't run very well, but the HC emissions are reduced while waiting for the catalytic convertor to light off.
John
