I am fixing up a K100 RS. It would start when I found it but that was about all. It is running pretty well now, especially at RPM´s over 3800. Under 3800 there is a slight vibration enough to make the faring buzz and the bike surges a bit but when it hits 3900 RPM it smooths out and runs like a rocket. Is this normal? If not any ideas? Thanks in advance, Steve