Talking to the head wrench at the local Yamaha dealer, they just set up a WR450 for a customer, they installed a FMF ti muffler, mid pipe and Power bomb header, he said the weight difference was 6.5 lbs.( the power bomb header was actually a little heavier that the stock pipe) he also changed the timing to YZ specs. He said the power is phenominal. He said when they checked the tourque on the fly wheel nut it was 15 lbs. He's got one coming in for himself, said he's going to do the stuff above plus remove the overflo bottle, and install a higher pressure cap. He's ordered a battery thats supposed to be two pounds lighter. so just with that he figures that to be about ten pounds, he said they weighed them at 262 lbs minus ten is 252 lbs. thats three pounds lighter than a KTM! Two of them are getting the WR'S the other guy is installing a YZ rear fender and removing the kick stand, figures maybe another two to three pounds saved. Intresting, I'am glad they are doing all this expermenting for us.