Twin Air air filter to suit Yamaha YZ 85 / 02 part # 152012 will fit RM 250 / 400 1980 also Pe 250/400 1980 -1981
RRP around $30-$40-00 mark
Inline fuel filters can be bought at most M/C shops MCs page 11/7http://www.mcsonline.com.au/index.php?option=com_content&view=article&id=80&Itemid=137
While your at it - remove the fuel tap from tank and clean the fine inlet stainer. If you want more fuel ( as they have a tendacy to lean out due to a small bore tap ) go up one size by drilling it out - or install a YZ tap