Advice on coolant line flakes

Can someone please offer some advice on this black paint/film like substance stuck to the inside of my sdr 990's coolant line. The pic is of the line between the radiator and the water pump. It feels like soft thin paint, not plastic or oily. I found it while doing the water pump rebuild that i decided to do simply out of preventative maintenance. Also did the balance shaft seal, cam chain tensioners and oil/filter at same time. Have had no coolant loss, no overheating issues and bike is running fine. Found the balance shaft seal was worn out and the front cam chain tensioner was fooked but that's another subject. There was a couple of flaky bits in the top of the radiator before i emptied it. Your help on this would be greatly appreciated. And Yes i did use the search button but couldn't find anything that i thought completely matched this.

You get a free card for once as it hasn't been mentioned for a while.....

It's sand from the casting process and a lot of 990's had that. When left it fooked the water pump seal.
Always check the coolant reservoir on a unknown 990 and see if there is black residue. If there is drain, put the hose on it and flush thoroughly!
Fill with new coolant and don't forget to raise the front of the bike to bleed properly.

Ok cool thank you. I just couldn't figure out what could be lining that hose like that as it certainly isn't oil. And thanks for the free pass, i was worried i would be yelled at .. Believe me i spent hours searching before posting.

I thought it was residue from the radiator cap's rubber seal. Soft and squishy.


Sarasota_Steve
08 990 SDR