Boring a 400ex

[sik02ex]

I have an 02 400ex right now it has an FMF slipon and k&n power kit im looking at boring it next but my question is what else should be done along with boring it (cam, bigger jets, etc?) and also what would the best size piston to go with 416,440 or somthin else if one is more reliable than the other??

[speedy400]

i 2nd this question..

[F-16Guy]

A good cam and a high compression piston are a must if you're going to bore your cylinder. As far as how big, that's a matter of preference. I have a 416, I love it. Some people swear by 440s, and others 426s. The reasons I went with the 416 are:
1. Unlike the 440, you only bore the sleeve, so if something really bad happens or you want to go back to stock, you're only out the cost of the sleeve and/or the piston kit.
2. I've heard quite a few people talk about reliability problems with the 426 because the sleeve is so thin after boring it .120 over.
3. Heat. The bigger you go, the more heat your bike makes. Ofcourse, there are solutions for this, but I'm trying to keep things reliable and cheap. Your budget may allow for this.
4. My bike is just a play bike. If you race, you may want the extra ponies at the cost of economy and reliability. It depends on what you use your bike for.

I think the bottom line is that anything is better than stock, it just depends on what you're going to use your bike for, and how much money you want to lay down.

[bklyn400ex]

my bike is just a play bike 2, i am also thinking about boring, and putting a hi comp piston and a cam, will i notice a big differenge, i already have a pipe, holes in airbox, groung welds. And also will going to a 416 ruin the reliability considering that i only ride twice a month and my bike is like 200 miles away from me, and i dont wanna be fixing this thing instead of riding it

[F-16Guy]

My bike runs perfect every time I ride it. If have the work done professionally, you shouldn't ever have a problem. If you do the work yourself, make sure of a couple things: 1. Buy a Honda Service Manual and follow all of the torque specs, etc. 2. Make sure everything is CLEAN before, during and after assembly. 3. Make sure all of your clearances are right (ring gap, valve lash, etc.), and all of your gasket surfaces are clean and true. If you have any doubts, have it checked by a good machine shop. If you do this, your bike will run forever.

[bklyn400ex]

was a 416 enough of a power increase, or should i go with a 440??

[honda400exrider]

with 11:1 compression, can u run regular gas (93 octane) ? and does the 10.8:1, and 11:1 have a big difference? cause thas not a big difference mathmatically... lol? THANX

if u want u can get a stock bore with a higher compression

[sik02ex]

so if i got an 11:1 440 kit and an all around web cam should i be ready to go with that?