I recently discovered the news that normal Euro 95 (Europe) fuel contains 5% ethanol (since 2013). I also discovered that this does dramatically change properties of the mixture and may need adjustment in the Carb jets, etc... My motor was not running very nice (just bought it) and I decided after messing around with it, to change to some special fuel from Total (Excellium 98, without Ethanol) and guess what...All problems I had with the engine have almost disappeared!!! However, I noticed some sludge in the Tank (l suspect it comes from the Euro 95, ethanol) and noticed that the fuel valve had a internal leak. I understood that this ethanol crap does react with water and/or oxygen or something and may seperate from the other parts in the fuel (very quickly the fuel gets old) and creates this sludge...and may therefore block small channels in the Carb. Even worse, ethanol seems to attack some specific rubbers (natural rubber and butyl rubber) - hence the leak of the valve?-, other rubbers are not prone to this attack (Viton and Nirtil Rubber). Some alarming news came from companies dealing with older bikes, claiming that since this ethanol was introduced their repair shops started to get full of bikes with serious fuel related problems...They even started a society to stand up against the acts in Brussels to stop the increase to 10% (related to politics and environmental, global warming stuff...)..- they seem to have never investigated the effect on Older bikes or Cars!!! Anyhow...my question is, does anyone know if the Yamaha WR400F, equipped with the FCR carb Keihin FCR-39H contains these sensitive rubber materials (butyl rubber or natural rubber) in seals / gaskets etc...Has anyone had problems with the additions of ethanol to the fuel? Thanks for sharing your experience!