Fuel resting in the float bowls forms a meniscus in tiny passagways. As the carbs are vented to the atmosphere, evaporation takes place at this area and deposits form, resulting in a narrowing of the fuel passageway. The slow jet orifice is usually above the fuel level and dried fuel deposits act to further narrow or even plug this restrictor.
Agitated, flowing fuel can cleanse these deposits if the buildup is not too severe and if they are not fully hardened. Humidity and termperature play a large part in both the build rate up AND the cleaning action, too.
Draining and coating the carb internals with WD-40 helps keep oxygen and moisture away from the metal surfaces that may instigate corrosion flakes. Although the WD-40 oils may congeal over time, they won't harden, and fresh gasoline will soften them enough to flow through the engine.
For the purpose of keeping just the carbs cleaned with gasoline flow through, a once a week run for a few minutes should suffice. However, the engine crankcase is also vented to the atmosphere. And, the internal formation of condensate each time the outside temp is cooler than inside, is more prevalent during short engine temperature cycles. Water in the oil is a very bad thing and prolonged contact of water with oil forms amino acids that begin to dissolve metal as well as promote internal rusting. To get rid of the condensate, the entire engine unit must reach a temperature sufficient to vaporize the water accumulation. An oil temperature of 160-180 degrees for 10-15 minutes is often enough to acheive this. Since the engine is air cooled without any means of temperature stabilization, the run time to achieve this varies greatly. In the summer, 10-15 minutes of operation may be all that's required. In the winter, at very cold temperatures, 30 minutes may not be enough!
This is why winterization proceedures exist.
hey TT.wd40 just once after the drain.as in good for the winter storage
Yes. For one winter. If you can plastic bag the carb bank after treatment, the better. Even better is if you throw in a small bag of dessicant and seal the plastic bag. That should be good for ten years or more.
TT, how long should I let it run and should it just idle or should I rev it?
If you rev it in place, remember it is air cooled. For just keeping carbs cleaned, 5 minutes at idle should do it, in order to keep the tiny slow jets clear. Seems unlikely you can resist reving it a few times.
However, then there is the oil temp, condensation thing...
Cheers,
