[charlie_nelson1]

i have an 04 400ex and was told when i bought it that it has a 440 kit on it but the cylinder says 397cc on the outside. i dont know what to look for on the piston. but i cant measure piston- to- bore i dont have the tool.

 

[alloutdoors]

i have an 04 400ex and was told when i bought it that it has a 440 kit on it but the cylinder says 397cc on the outside. i dont know what to look for on the piston. but i cant measure piston- to- bore i dont have the tool.

Here is a 440 kit, note the cylinder/jug change, 400EX Big Bore Kit | eBay

Here is a good place to begin browsing some 440 info http://www.hondaatvforums.net/forums/performance-modifications/26617-400ex-big-bore-kit.html

 

[SlammedRanger]

Well if you have the head off and can see the piston is it a flat top? If it is its almost certainly a stock piston. Stock bore is 85mm and a 440 kit is 89mm that much difference could be measured with a tape measure straight across the bore. The proper way is to use dial calipers but if it is a 440 it will be pretty obveous. Alot of time people claim big bore kits but there isnt anything done to it at all. Which i dont undrstand because if someone says it has a 440 kit i turn and sprint in the other direction. I am yet to see even one person do one right and you will be changing headgaskets weekly. My .02

 

[M_Quick]

Harbor freight has cheap calipers for a couple bucks. I wouldn't recommend them for machine work but would certainly measure your piston.