I have a 1980 GS550E and have considdered k&n's before. I have enquired about it several times to local old bike experts. One was a very good shop that works on old bikes, he said not to do it, I was surprised because I was offering him the job. The other person was a former team suzuki mechanic and also said not to mess with the air box at all, it will only run badly. Unless you are changing the exhaust system and it requires re-jetting you are better off with stock jetting and air box. He said it is really hard to get them to run right with K&N's and new jets.