No it shouldn't take much. Carefully remove the head, making sure not to loose the small shim that sits between the head and the top of the sleeve. It may be an idea to use some cotton buds to remove any gummy residue, and then flush the rest with fuel. A few small squirts with the fuel bottle should do it.

If you want to get ALL the gummed up stuff out of the engine, you are going to have to do more though, as this will just remove the gunk from the combustion chamber - not the rest of the engine. If you want the engine to run properly you will need to do the following...

* Remove the engine from the car. You will also need to remove the exhaust manifold - be careful, there is a small paper/metal gasket between it and the engine. Try not to bend or break it.

* Remove the pullstart. When you remove the pullstart make sure you get the inner spool in one piece. Don't just remove the four screws and yank it. Undo the screws and carefully slide a blade or small screwdriver between it and the backplate. You want to get the housing AND the spool together. There is a spring between the two makes the cord recoil) - if you pull the two parts it will coume out of it's mount.

* Remove the backplate.

* Remove the engine head.

* Remove the carb - note exactly what position the carb is in (take a pic so you can set it properly afterwards)

* Clear out the gunk with fuel, cotton buds and afterwards ARO (after run-oil). The ARO will displace the fuel and prevent it gumming up again / rusting. Also check the carb for gumming.

* Put the engine back together. If you have any high temp sealant use it to seal the backplate and the carb to the carb neck.

You may not want to go through all this - clearing the combustion chamber MAY work, but if it was my engine this is what i would do.