Well I have been doing a lot of research and reading up on the different builds for the 400ex. I picked up an 06 400ex that’s pretty much stock except for having a jet kit and a knock of brand k&n filter. It dose however have a great set of moose racing nerfbars with the heel guard, and moose and monster graphics. I have a bout 1900 in it, I thought it was a good deal for an 06.

I have decided to go with a .040 over hi compression 11:1 piston, I think that would be a 406cc, stage 2 hot cam and DID cam chain, hmf slip on pipe, dyno jet kit, and I ordered this used air filter and aluminum adapter plate that dose away with your stock air box, have you guys heard of anything like that?

I was also thinking about doing a port and polish and grinding out the welds in my header? Would I see any gains or would it be a waste of time. This will be my first rebuild on a four stroke engine, so just looking for advice or pointers, maybe something I have missed and maybe a starting point on what jet size to use. My buddy has an 01 660 raptor, I’m hoping to be able to hang a little better with him, but will see.

 

any advice?

 

I pulled the head and jug off to day, everything went smooth except for the cam chain. How to you get the cam chain off the crankshaft, right now I just pulled the chain tensioner and slid the chain off the cam and now the chain is still on the crank. How do you get it off and put the new one on?

 

I don't think you can without splitting the case. At least that's the way a 300ex is. You can replace the cam but not the chain without splitting the case.

 

　
I think I found my answer, I have to pull the right side clutch cover, I believe that is right.

 

Is the chain bad? Most times guys will do a top end rebuild and not get into the bottom.

 

I thought I would go ahead and change it since I’m replacing everything else. But is that correct, is that the only way I can get the cam chain out? Pull the clutch cover off?

 

anybody?

 

I have a 400ex but cant help you on that you may want to check out exriders.com theres alot more help over there and alot of ex gurus im sure someone can help you out

 

with that pistion you will need a spacer plate so the valves dont hit the piston