I have a 06 kfx 400. every piece of aluminum u can buy is on it. ct exhuast and jet kit. air box with 250r kn filter. have purchased new hotcams and springs but not installed. considering the 434 big bore kit or the +5mm stroker crank. or possibly both. necessary? thoughts/comments? also have 1000 rpm rev box. running the 13 42 sproket setup. love that ratio. think i would like the eldebrock carb also. what are the most popular and effective mods for hp and torque gains?

 

I would get a carb first. You wont notice the full effect of the cams without it since you arent getting enough air to the cams or then the cylinder, so carb first, when you have the head off a minor port/polish would help a little too if your comfortable doing that. Also if you are going with that much motor you really need to get new valves the stock ones can break off and ruin your motor, I see you already have springs which is good you need those with a rev box.

Check out the FCR39mm carb off the yfz450's too its a great upgrade but a little harder to install. Personally I'd go stroker over big bore both of them help add a lot of bottom end power, the cams change where the power is made, since you bought hotcams you will already be adding bottom end power, it really depends on your budget but I'd for sure get a carb for it. check out z400central.com you'll get answers for all you want to know.