01 400ex rebuild questions

[dodgeram14jr]

So I raced a 5hr team harescramble this past weekend with my 400ex. Alittle less than half way threw after we switched riders I noticed it started smoking white alittle out the exhaust. So next time around we checked the oil and it was low so we added some and seemed to help alittle. The plug is black and carbon covered. My question is should I just rebuild the top end or rebuild top and bottom end. If I rebuild topend only I'm gonna atempt to do it myself. I have the quad for about 3yrs now I'm not sure what the previous owner did maintenance wise just looking for opinions on to redo both or just topend. Any help is appreciated Thanks Dean

[DragonGunner]

No need I see to mess with the bottom end. Probably just next size bore for top end and parts and good to go.

[dodgeram14jr]

Is the topend hard to do?

[400man]

top end rebuilds are not too difficult. if this is your first one id look into a repair manual like clymers. and get all your tools together before you start. when you have the cylinder off, check and see if there is any play in the rod up and down.

[dodgeram14jr]

Yeah this is my first rebuild. I found a post on here where the guy explained step by step on how to do that and I printed that out and was going to follow those instructions.

[joker11]

I had never done an ATV before. I found it to be really simple. I watched a youtube video by Partzilla first. That guy does a good job on the TRX400EX top end rebuild. He also analyzed what the problem was. I thought it was a good catch too.

For me, the hardest part was putting the cylinder down over the piston rings. On a chevy engine, you put the piston down into the cylinder and can use a piston ring compressor and a dead blow hammer. So I was frustrated by using my fingers to get it all together.

Easy peasy on everything else.