I use eagle one etching mag cleaner. Just spray on waite a few minutes and hose it off, works well on all parts of your dirty quad. Just be carefull not to spray it on chrome as it will discolor it quickly..
http://www.eagleone.com/pages/...?itemid=1001&cat=5006
It works majic on rusty,oily,greasy, and brake dust cover'd parts..
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91 trx250x,60 over,custom port job,stainless valves, piped and jetted.