Rebuild ?

[kcalexan83]

My 400ex is starting to smoke. So I figure I will probably bore it this winter. Probably to a 406. I want to keep it reliable and run on pump gas. Kinda a budget rebuild. I already have a hotcam stage 2 for it. That is the only motor work done to it. I guess I just want to know what all I will need or your suggestions. Thanks, Kyler

[honda400ex2003]

a 406 will be a nice addition for you then with the stage 2. depending on the gas you want to use 11:1 93 octane, 10:1 89 octane is your choices. you could probably get away with 87 on the 10:1 and 91 with the 11:1 if that is what you need to run cause that is all you can get at the pump. anyway either one you will be happy with in my opinion. steve

[brian76708]

416 IMO still reliable same cost and reliable. i suggest , valve seals, 450 cam chain, and new cam chain tensioner

[coreyownz]

they make a 406 bigbore? id go with the 416 its plenty reliable if put in right and broken in correctly

[Pipeless416]

yes, a 406 is an 86mm piston and bore. why not save a bore? the gains from the extra 10 cc's will be minimal.. i agree on the 10:1 compression though.

[Dave400ex]

Kyler mine had the 416 and ran good and reliable. It had the 10.8:1 and I always ran pump 93 with the cam. The valve seals are a good idea and I remember reading about the chain after I did mine.

[VTredneckgames]

I just went through the same thing. I had the head rebuilt, valves ground and new seals installed. I bored mine to 406 and I am running 10:1 but with the stock cam.

I dont see any reason to go on up to 416.

And I also swapped to a CRF450 timing chain. Mine acted fine length wise, but you could see where it had started slapping the sides of the case some. I was intimidated about swapping it at first, but it really is a very simple process. The hardest thing about it was sitting there taking the time to clean the old gasket off.