People that only go by the factory manual will do that and ignore any other ideas- the manual was copied for this thread by another poster.
The one mechanic wrote that he left the carb float bowls full all winter for the older non-vacuum petcocks, and left the petcock on all winter so as the fuel evaporates in the float bowls, the float valves open and refill the carbs, to keep the carbs from drying out. He also left a small electric light (old style hotter bulb) turned on below the engine, at least during the coldest weather, to keep the engine warmer and dryer (he lives in Canada). He left the batteries in the stored bikes, attached to a small solar charger on the outside garage roof, hidden from thieves. Make sure you check the engine oil and the amount of fuel in the gas tank in the spring, for the slight chance that a float valve sticks open and maybe floods the engine with fuel if you left the petcock always on.
For the newer vacuum petcocks that only open when there is engine vacuum while the engine is running (for more safety after a crash or when the bike is stored), it seems best to use marine fogging oil by spraying it into each carb while the engine is running, then run the engine out of fuel to drain the carb float bowls. Either leave the gas tank full of stabilized fuel, or empty the gas tank completely and slosh some 2-stroke oil around inside of it to coat the bare steel.
Another method is to get the bike out on some warmer winter days and ride it at least 10 miles, to fill the carb float bowls with more stabilized fuel, and to evaporate water out of the engine. If you use Seafoam instead of Stabil to preserve the fuel, you are also cleaning the carbs.
"Until he reached thirty, Randy felt bad about the fact that he was not socially deft. Now he doesn't give a damn. Pretty soon he'll probably start being proud of it." from Neal Stephenson's Cryptonomicon novel (1999).
Last edited by Jeff in Kentucky; 11-10-2012 at 09:25 AM.