I just picked up an old ex500 and I'm getting it ready for the road. I went to check the oil level and have found that the window is soild black. I'm not sure if it has been over filled or if the old oil is just sticking to the window. But either way the oil in there is pretty nasty. This is my first project bike and I dont know the ends and outs of these tiny little motors. Is it ok to run an engine flush through it to brake up some of the gunk? In cars I normaly run through the flush, fill it with cheap oil and bring it up to temp, then change it again with better oil, will this same process work or will I do more damage than good? Any help would be great, thanks.