I couldn't find very good info on this when I searched so I decided to post my results after weighing some 07 WR450 parts on my local FedEx and Post office scales (both scales had identical readings) : Silencer: Stock 2007 WR450 silencer: 7.35 lbs FMF Q4 Titanium: 6.15 lbs Choosing the Q4 Ti saves you exactly 1.2 lbs over stock. I would like to know how much the Ti actually saves over the non-Ti version. Probably not very much. Shock Spring: I changed my stock WR450 spring to a Ti YZ spring. Stock WR steel: 3.6 lbs Stock YZ Ti spring: 2.3 lbs 1.3 lbs saved in a place that probably isn’t very noticeable while riding. Battery: Stock WR450 Yuasa battery: 4.6 lbs TurnTech 2.5 amp battery: 15.4 ounces or 1 lbs 3.6 lbs lighter than stock! Great bang for the buck especially while lowering weight in a very high location. Unfortunately I’m not sold on the 2.5 amp yet for my 450, it never starts like I want it to (although the easiest kick and it fires right up) so I may change to the 5 amp. Bars: Stock ProTaper 2007 YZ/WR bend: 1.5 lbs Flex bars – Woods 12deg bend with damper crossbars: 3.35 lbs 1.85 lbs extra at the absolute highest location on the bike. BUT my wrists love the flex bars so I’ll stick with them. Anything to prolong how long I can ride into the future.