Heat the upper cylinder with a torch first and use a little lighter fluid in the carb to get 'er going. Some foil tape over the fins might help... Or, like motorboy said, just start it... OS's come with a pretty comfortable fit to begin with. Something like a squeaky tight Rossi, Jett or older K&B performance engine might need more attention but you should be OK with an OS.

Bill Vail
www.RCScreenProtectors.com