XR400 upgrade advice

On dust, the airbox modifications won't funnel airborne dust into the box. Your filter won't be exposed to any more dust than before. Water and chunks of stuff will have an easier time getting into the airbox without the baffle but dusty air will only enter the box as fast as your carburetor asks for it. Some folks go as far as to apply a netting or coarse filter over the entrance to the box to keep pine cones and mud chunks from being inhaled.

I hardly ever get into third gear on trails, never out of third in the woods. Why would you want to? You would be shifting all the time, and the big power of the 400 allows you to lug the engine. Your best bet, and what I did on my last big XR, is to drop a tooth from the front sprocket. This won't require you to modify your chain, it is cheap from rockymountainatv.com for 10$, and won't cause rubbage issues with the rear chain guide like a larger rear sprocket can. Also, the smaller front sprocket can be switched out pretty easily to allow you to change back and forth.

Don't bother changing the muffler or header pipes out if you are a woods rider. Studies have shown little to no benefit from aftermarket xr400 exhaust systems except they look cool and lighten your wallet. What little improvements there are almost always occur at the top end with the negative impact of big noise. The stock exhaust is really very good.

Do a search for the Gordon Mods. It will really make a big improvement for little money. Even if it weren't for the cash issue, there is very little else you need to do. As you can see from my recent post, I had some of the same fears as you so I waited a year before changing things. I never believed the improvements would be so big.

I never changed the gearing on my '97 XR400, but I did put a White Brothers R4 pipe on it. The pipe was one of the best mods I did to the bike. It definitely added a little more "pop" in the bottom end. It was quite a bit louder than stock, so I put the special R4 quiet core in it and was able to pass the 96db sound test at my riding area. I recently sold the pipe to my brother-in-law and he loves it too. I didn't do anything differently with the head pipe though. It was stock. A lot of guys are putting the Mikuni pumper carbs on the 400 with great results as well.

I agree with the note about the exhaust they generally just improve the top end (experienced this with a friends 400EX, same motor, it killed the bottom but gained some mid to top which is what he was looking for) and of course the noise issue, clean up the sloppy welds on the header pipe were it is joined to the mounting flange, of course if you read the Gordon Mods it will state that.

here you go http://4strokes.com/tech/honda/gordmods.asp

On my '00XR4 I'm running 14/47 gearing. I initially swapped the front for the 14 and rode it like that for a while. Big improvement for woods stuff. Then I got into riding the hilly off camber stuff that my friends around Los Alamos ride and I decided to up the rear to a 47 and that's how I've run it ever since. Top end suffered for sure, as I don't like to run it over 40mph, but it's great for tight and technical stuff. You won't have to alter the chain for the 14, just readjust it's slack. The addition of the 47 rear required me to add a 2nd master link.

Derek