I am interested in putting a 440 big bore kit on my Honda 400ex. I have been researching the different brands offered and such. I found the Namura piston and have never heard of that brand. Has anyone ever heard of it, used a Namura piston or have any thoughts on the 440 big bore kits? Thanks

 

You could get the Athena kit. It is very reliable and increases the powe a lot. I have got one on my z400. It comes with everything you need.

 

i heard 440 kits on the honda 400s were not worth it, unreliable..this guy i talked too that had one said it was a menice for him...i think its all in how you build them and who builds them, i do love the athena kits and know many people with them and have no problems with them at all..its all in what you want and how you go about doing it, build it right and you shouldnt have any problems!! =)))

 

If I were you, I wouldn't go with the 440, I would start out smaller, like a 416 or 426, so if you blow it up and need a fresh bore for the rebuild, you have room to go bigger. I also have ridden both 426 and 440EXs and I have to say I liked the 426 more. It had power everywhere when the 440 pretty much only had low end.

 

Welcome to the forums. [img]i/expressions/face-icon-small-smile.gif[/img]
The 416 is as fast as any bore and very reliable. My daughter won championship #5 on her 416.
Yes, Athena makes a good product also. She ran the Athena 480 on her CRF hybrid. That was championship #6.

 

the 440 kit comes with a new cylinder and everything so if you blow it up you can always go stock again. i installed on a while back and did away with the decompression release and installed a big gun exhaust and a stage 2 jet kit and that 400ex really hauled and had a big torque increase too.