What would happen if someone were to put an xr400 camshaft in a 400ex? I read an old ad from Honda that states that they changed the cam to produce more torque. I read somewhere else that the xr400 cam will fit and even has a compression release lobe? I heard that it is better to go with a stock cam because the aftermarket ones just weld metal on and regrind it and at that point, they have a tendency to wear out much quicker than the stock ones? I lied, it is several questions. Sorry, but thank you.
Mike Mazza

 

I have a White Bros. cam that I bought through my local shop, when I first asked them about a new cam, they suggested an XR400 cam. It fits perfect, has the compression release lobe, and is quite a bit cheaper than an aftermarket cam for the EX since it is stock for the XR, I don't think it increases performance as much as some of the other cams though.

 

I've read somewhere that you can use a top end gasket from a xr 400 on a 400ex to boost compression. The xr400 gasket is thinner. Has anyone tried this?
Bruce
2000 Banshee
99 400EX
99' Wolverine

 

Hi Mike!

Yea, that's more than one question, but I guess I'll let you off -- just this once :-)

Yea, the XR cam would fit -- you'd have to yank off the decompressor since it's different. But it would give you much performance gain.

Hardweld camshafts get a bad name from some people because they've had them wear quickly. Billet cams will have the same problem. The reasons a higher lift cam wears really quickly in some cases are:

1. It's higher lift! Puts more pressure on the rocker and cam lobes.

2. Not installing new rockers with a new cam. Ya gotta do it, or the new cam will wear.

3. Running synthetic, or crummy petroleum oil. Yea, yea, I know I'll get screams from synthetic lovers out there -- sorry guys, call the cam manufacturers, they'll tell you.

Actually, if it's done right, a hardweld cam has a thicker coating of hardfacing material than a stock cam does, so in theory they should last longer.

In the 400EX we have one other thing to deal with. The Honda RFVC head design uses 8 rockers to open 4 valves -- really convoluted, but it saves room and flows like a big dog! Anyway, because of this design, increasing lift and duration on your cam can greatly increase the amount of pressure on the rockers. Thus, worn rockers, then worn cam -- yuck! The solution is hardfacing the rockers at the same time you get the higher lift cam.

Thi$ get$ $pendy! Typically costing much more than a 440cc bore kit! Yikes!

Okay, now for the good news! The 400EX head flows REEEEEEEELY well stock. In fact, it flows better than the stock displacement engine needs. So, in most cases, any changes in the head can wait till after you bump displacement!

Sorry for such a long answer!!

Pam

 

Oh, yea, almost forgot! Bruce,
the XR400 headgasket is the same as the 400EX. No difference in thickness.

Pam