Rebuild time

[Maxx Racer]

I think its time to rebuild the engine on my 400EX. It was smoking when I bought it and my last ride I think I finished the rings off.

I am going to rebuild it, I've never rebuild a fourwheeler motor but I know what I'm doing when I get inside any engine (I drag race I've built plenty). So I was hoping I could find some help on here.

Where is the best place to buy parts? I havent been able to find a real solid place for parts on-line maybe you could share with me.


I'm going to rebuild it, and I dont think the 440 is for me, I don't need it. I'm not trying to be the fastest, I just like to go out and ride. I want to run it on pump gas, but I can pick up some higher octane gas if I need to.


My plan is to have it bored and run a 416 piston @ 11.1. Are there any write ups from people who have info on everything I'll need to go 416 with it?


If I'm in the motor I might as well put a cam in it. I have been looking at stage 1 cams. I'm not looking to race the bike, just a little bit more. I'd prefer to keep the stock rockers and valve springs if I can.


Last are there any websites or books I can buy that have the torque specs or any other info on these engine?

[Ruby Soho]

that bore/CP sounds good, go with the stage 2 cam, the stage 1 is based for stock bores and slipons etc... low end. youll be happy with the stage 2.

with hotcams you can keep your stock valvetrain, theyre made to use the stock parts.

i think in the articles section of atvriders has the torque specs

[Maxx Racer]

Alright Stage 2 sounds more like what I need then. I'll check out the articles too, thanks for your input.


Do you have any online stores you like better than others?

[TRXRacer1]

Stick with the stage 1 if you're looking for more midrange power. The added duration is not just for stock engines. I'm basically running the same combo you are talking about and love it for my woods style of riding. I chose the profile to keep the power down lower in the RPM's.

Here's a little write up that will shed some light on what to expect when you open it up. It's as basic as a 4 stroke engine can get.

416 build from WI ATV Forums (http://wiatv.invisionzone.com/index.php?showtopic=602)

[Maxx Racer]

Thanks for the link. Good stuff!

[Maxx Racer]

Wow, this might not even take me a day. I figured it took more work than that LOL I need to put the heads back on my car and then it will the the 400ex's turn. :D