Well, if you dropped both from the same altitude, the four stroke should fall faster....ha ha ha...sorry, couldn't resist.
The Honda uses a cam driven fuel pump and it is possible that it could leak gas into the oil. Look under the valve cover.
Many of these engines just plain run pig rich all the time though when the thermostat is stuck open and unburned fuel sneaks past the rings as it is washing down and destroying the cylinder walls to contaminate the oil. After that is allowed to take place for a while, the compression will be low and power will be down. As this occurs, the combustion will, again, be very inefficient and even with a properly heated engine, unburned fuel enters the crankcase.
