The clunk for most gasoline engines is usually slightly larger and often differs from a nitro fueled engine by having a felt like covering over the clunk as well as a screen filter at the mouth of the clunk. This aids greatly in getting good fuel flow as the tank nears the empty mark. With the felt filter, you will get the last drop of gas out of the tank. Check with your local lawn mower shop for possible sources of fuel line suitable for gasoline as well as tanks and clunks at usually a lower price than the local hobby shop.