I have heard that an xr400 cam can be used in a 400ex to provide an increase in power over the stock cam. I recently contacted my local honda dealer and asked if this was possible. He responded that it was not likely. I was just wondering if it is indeed possible? If so, what effect does it have on the 400ex, how much trouble is it to swap cams, and can the stock valve springs and rocker arms of the 400ex be used with the xr400 cam.

 

I have one in my 416ex. You can just switch the cams. Stock rockers and everything is fine. You won't get a huge noticable difference but what the difference is that the 400ex has so much bottom end power it just kind of moves the power band up through mid and top. Where the stock cam has alot of low power. White Brothers rev limiter is a must for the cam. This way you can use the upper power.

 

so its not hard to change the cams? How much is one of the xr400 cams? also how much is a rev limiter?

 

Thanks for that information. My honda dealer just looked at me fuuny when I asked him about swapping cams. I think I will try the xr cam now.

 

The XR cam is pretty much just a bolt on. No modifications or nothing.
You can get the xr cam from hondaservice.com for about $110 The rev limiter runs about the same price.

 

how much low end does the xr cam have? I heard it loses a lot and I wanted to find out from someone that is running it.

 

I am running one in my 416ex, too. I do not know what losses it had, but with a higher compression piston (11to1), you gain back all the low end that you lost. Mine is way more powerful than before, but I did the 416 and the xr cam and of course, rejetted.

 

I'm running the XR400 cam in my 425@11:1. I haven't noticed any losses in the bottom. It seems to have beefed up the midrange, and gave it a tiny more up top. The kicker is, being a stock Honda part, it shouldn't cause excessive wear on the rockers like the aftermarket cams have been doing.