I have a 1979 KTM 420, I'm restoring and I noticed the plastic air-filter cage/top cover are very brittle does anyone make a reproduction. The top cage cap that the mounting bolt goes thru is really bad. Also how do you get the air filter mounting bolt thru the cage/filter, the air box is small and the long bolt isn't perfectly straight. I'm sure, I'm doing something wrong. Thanks for the help and any other 1979-80 KTM 420 tips would be great.Thanks frog