well my 400ex still runs as of right now but for some reason im lacking some major power and i think its my piston comprestion cause i think my rings are shot cause i burn oil i also have a leaking carb anbd the idle screw and choke are broken......but im getting it all done this weekend and getting a wiesco 11:1 piston put in and was wodnering if im gonna see any bnig improvments in my quads power right now i have a 155 main jet.....yoshi slip on...SRP rev box....K&N filter as far as engine mods right now but ounce my rebuild gets doen and carb fixwed will i see any big differences?

 

if you have the money i would highly recommend the 426 big bore kit. i have it and i have put about 20 hours on it since the rebuild. make sure when you get the piston go ahead and taps the head bolts out and make them bigger and go ahead and get the Hocams stage 1 or stage 2. but for your mods i think you will see a difference because it was never running right if the carb has been leaking and your rings were shot. Just my opinion about the big bore kit too