I currently use ATF too. It just happened to be in the garage when I noticed my carbs were low. The carbs work great.

I have also used 10W40 10W30. I can't tell much difference.

You could probably use vegetable oil (Im not going to try it). The oil doesnt really oil anything. Its just a liquid damper.

Thanks - ATF it is!!

cant diesel engines run off vegetable oil? i wouldnt reccomend putting that in... sorry got side tracked reading this thread

Over the years I have read of guys running everything from water to brake fluid in the dampners. The builders of the carbs say 20w . Personally I have tried ATF ( 5w) Misteray oil (5w) as it turns out and a mixture of light oils of different weights. For me living in the north west I have found that what the makers of the carbs are correct 20w works the best . I had a stumgle off ldle that I thought was ignition . Drove me nuts . After a long time trying all sorts of stuff , I finally used the 20w . The stumble dissapeard . It may not work for all but try 20w , I found the fork oil at the cycle shop . for what its worth . Gary my 5c