Need Some Help/Advice on 400 ex

[EVANSTURF]

I hav a 2003 400ex and need a lil more power. I was wondering if anyone would tell me if the big bore kit is worth the money and is it really a big difference. I would like to add a exhaust kit with and need some advice on which one also I was thinking a white brothers or a fmf. Any imput would be nice

[Ida_Mann]

the big bore 440 kit turns it into a torque monster, and if you want to race, or feel a lot of regular riding power out of it, I wouldn't suggest it.  Better to go with a smaller bore like a 416 or so if you really want to bore it out.

I would suggest that you go with a full exhaust system and see how you like it first,,,maybe a differnt intake and rejet it all to match,,,,you will notice a ton of difference that may change your mind about getting it bored.

Id@