Carbon in the frame.

[spanner boy]

As the engine work continues could somebody explain to me the mechanism under which carbon granules get into the fame. They are only on the side walls. The oil is clean and there is no sludge. There is also no sign of grey paste in the transfer port, which I take to be a good thing. I have had problems with the Scavenger pipe which was disconnected and also finally had a sheared adapter (trying to source a new one).The plan now is to try and clean the inside of the frame (brake cleaner a clean rag and a large screw driver is the plan) before getting it all back together. The bike currently runs Rotella which I'm guessing may be part of the problem. The question is will these granules damage the engine if they are drawn into the cards?