big bore kit for 400ex

[doin it in the dirt]

Been doing some reading on this. I got a 2001 honda 400ex, runs great, have thought about putting in a big bore kit, but read that I shouldn't bother unless I have a blown engine....any thoughts on this? I have read alot of people have had problems with there quad afterwards...let me know what you think

 

[Mikehunt]

On an air cooled engine the extra temp and thin cylinder makes the engine run alot warmer

 

[CountryRider]

The idea of having a big bore kit is sweet you do notice power increase. But the thing is why get your stock cylinder bored all the way out when somehting might happen then ur screwed, u no longer would be able to use your cylinder even sleeving it will become harder. If i where you i would get an 86-87 mm bore size which will still run you at a tad bit under 440cc... running at 11:1 compression..

You will still notice the power