[steve74]

Hi guys, a long time since I've been on here but I've been searching the net and I can't find the info I'm after. To make a long story short I have a 2005 crf450r motor in a road race chassis and I have done as much as I really can with the motor while still keeping it 450cc. The one area I haven't tried playing with is the exhaust. A friend custom built the exhaust using a standard header flange which after an inch is welded onto a 2 inch pipe which then runs under the bike before expanding onto a Ti4 muffler. Now this pipe was built in a hurry with no science applied and I now want to build something that will complement the engine mods. Does anyone have any suggestions on diameter or length or can someone measure an fmf , pro circuit or similar for me. A bolt on pipe is not an option here.