[Vwdiesel] cleaning carbon clogged rings without disassembly

[mikitka]

I would try putting some Lube Control down in each cylinder and letting that
soak for a while. This stuff is great at dissolving carbon. Plus it will not
hurt the engine at all like a normal solvent would. It is made to run in
your oil to help keep things clean. It has been around for 40 years and is
just now really getting marketed.
http://www.lubecontrol.com/lube.htm

Nick