Just wanting to hear from anyone who has real world expierences with big bore kits
on these 400s. How much power can you really expect to get out of these motors
and how much will it take away from the reliability. Im not expecting it to perform like a 450r
or a yfz450 but a little more power would be nice.

 

well i think you need to look at the athena 434 kit .it will bring you up to the yfz 450 power

 

The 434 kit is probably the best kit for the reliability and you'll be right with a yfz or 450r,if not have abit more power.Now the yoshi 450 kit is a powerhouse and will beat any stock yfz or 450r easily,but its not as reliable.

 

I have the Yoshi 450 and it rocks. Yfz-450s are no problem....

 

Thanks for the help. these are pretty awesome quads off the showroom floor and
ive heard that they respond really well to mods.