Thank you for requesting this report!  Let me start by letting you know that I'm a HORRIBLE typist!  Even more horrible on MS WORD!  I'm extremely rushed to write this as I have to take time away from business projects to do it (not too mention that it doesn't bring me a penny!).  However, I feel I would be incredibly selfish NOT to share this information with other XR fans (I love XR's!!!).   I hope this information can help you get more fun and pleasure out of your XR, while at the same time save you money and something even more important (your time).

LET IT BE KNOWN THAT THERE WILL BE TYPOGRAPHICAL AND GRAMMATICAL ERRORS ABOUND!!!

Let's get started.  Not to bore you but to get this right I have to share a little bit about me and more important; my riding desires and situation, ok?

I love XR's.  My first bike was a CR125 and it was great.  Except it was loud and pissed off the neighbors and anyone within a mile radius that you rode it.  It vibrated like crazy to the point that bolts would fall off every few rides.  Mixing gas was bitch on long rides and the power was so unusable for my needs that I might as well been riding an RD400 with knobbies.  Fouling plugs was also a nuisance.  Come to think of it, that CR125 was like a high maintenance girlfriend!

The biggest problem with the CR125 was that

1) Where I live I have to ride anywhere from 10 to 30 minutes to get to the dirt.
And
2) If you have a bike with a plate your riding opportunities literally double and triple!  The CR was great (I thought) because I never even knew what an XR was.  One day this all changed when I bought a 1982 XR 200R.

I couldn't believe it!   Exhaust note so quite you could ride anywhere and sounded totally cool to boot!  Super usable power for the type of riding I do.  Just put gas and oil in it, adjust the valves and clean the air filter and you could literally beat the living day lights out of it and it just wouldn't quit!  Over 120 miles to a tank, unbelievable!  I didn't even have a license and I'd ride around on the street all over!  I thought I'd died and gone to dual sport heaven!

Areas I'd ride that we're super slippery and/or rocky where the CR125 would handle like a wounded giraffe trying to escape a lion, the XR would just motor!  Long story short; I NEVER BOUGHT ANOTHER 2-STROKE AS A PRIMARY BIKE EVER AGAIN! XR's FOR LIFE!   That was over 14 years ago…

Before I get into the MODS and experience with my new Y2K XR 400 let me preface it all with where I live, what I like to ride and at what altitude.

Currently I live in southern California.  The riding I like to do is all the stuff the XR's and their quick steering and extremely tractable power makes them excel at, in addition to the dual sport aspect which is a whole other topic that makes 4-strokes so much more fun.

I ride primarily trails.  All kinds; fast hard pack, sandy, whooped, rutted, rocky and the super technical.  Also fire roads, difficult/un-maintained ones loaded with so many rocks you'd think bombers had been dropping them in all night; the kind of stuff a professional 125cc motocross bike is incapable of making. Seriously, I should email you pictures.

In the summer time out here it gets extremely dry dusty and slippery.  In many cases it's like riding on marbles and XR's do very well.  It's not uncommon at all to see XR 400's out hill climbing 250cc two strokes.  It's a sight to see as I used to always bee the one that said I'll out hill climb any XR on a 250cc motocross bike.

The altitude I generally ride is 3,000 to 6,000 feet.  If I go somewhere like Kennedy Meadows where camp is at 7800 and you ride to 10,000, you bet I'll rejet (I just wish I could rejet my lungs for the altitude!).  The majority of the riding I do requires to ride the street for 15 to 30 minutes therefore a plate is mandatory (this has other advantages as well).   I also do a little gray market riding as well (Shhhhhhhhhhhhhh!).

TO ME, LIVING IN CA, HALF THE POINT OF OWNING AN XR IS TO HAVE A PLATE ON IT!

MY PERSPECTIVE ON MODS FOR MY NEEDS (your needs may be totally different than mine!)

When it comes to mods I take a little different approach.  Most guys just start spending money with the intent of increasing power. In this department my goal was not to increase power, but to increase usable power based on my needs (my needs may not be your needs but if they are you are in luck!).   My goal was to increase power primarily in the low end and mid range without losing ANY top end.  Reason: the low end and mid range is what makes the XR excel over a 2-stroke in many situations.  To me it's not about power, it's about usable power.  It's better and faster to ride a bike where you're using up every drop of power than it is to have a bike where there's too much power and you find yourself backing off in situations.

I was also looking to keep the bike as quiet as possible.  Not necessarily decibel wise but "irritating to the ears" wise. What do I mean? It's simple.  Ever heard a 104db thumper and then heard a 100db 2 stroke.  The thumper is technically louder but the 2-stroke is far more harsh on the ears.  This played a big role in the exhaust systems I ended up with.

ARE WE EVER GONNA GET TO THE MEAT N' POTATOS?

Yes!  In Just a Moment!  First let me share how to save hundreds on your next bike with almost no effort at all and keep salesman from wasting your time (which they love to do!)

When it came time to buy my new 400 I pulled out my trusty YELLOW PAGES CD ROM and got the phone number and fax number of every HONDA DEALER within a 90 mile radius of my house.  I then faxed a letter to the owner with all my contact information that went something like this:
 
 

At the time (back in October) $5700 out the door was pretty unheard of.   I ended up finding one dealer that actually sold me the the bike WITH THE PLATE for only $5700 out the door.   He was 60 minutes away.  If anyone in Southern Cal needs a bike I'll be happy to go with them and secure these same kind of prices.  In addition I could have got the exact same price FINANCED!  Needless to say you can bet I'll be doing more business with this guy…
 

NOW FOR THE MODS!

When I first got my bike I immediately removed ALL THE STICKERS.  Even the 400R lettering off the seat!  You can accomplish this by using a towel, stiff brush, nail polish remover mixed with any super aggressive industrial cleaner.  Don't worry.  The paint on the seat won't come off.  Just go slow to make sure your solution is working.  It takes a while but is worth it.  I just don't want my bike to stick out like an XR on the street to cops.   I want to be as low profile as possible.  In addition it's funny seeing people in the mountains stare and try to figure what it is and ask dumb questions.  I like it when people think it's a 600!
 

OFF WITH THEM THAR BLINKERS SON AND GET A REAL TAIL LIGHT!

The next thing I did was remove my rear blinkers before they were removed for me unwillingly.  I then got rid of the baja designs tail light and rewired a brake light into my stock tail light (it's real simple, the filament is already their just make a bead of solder and run the wire). Mounted the plate right on the fender.   I'm amazed at how few XR owners do this.  Don't you just love that pressure sensitive rear brake light switch from baja designs?  Still haven't got a fix it ticket yet!

UPDATE:  I hate the Baja Designs tail light because I ride hard and crash a lot and it sticks out way too much off the fender.  In addition, I found that the stock tail light blows bulbs like crazy from the pounding of the bike.  However, if you run the stock tail light bulb in the Baja designs tail light it will hold up substantially better.  Personally, I think the stock set up with rewired is the only way to go.
 

MAKING DUE WITH STOCK "CRAPOLA" XR SUSPENSION

Next thing I did was set the sag at 4 inches and click up the compression dampening.  If you think the XR has suspension (even if you weigh 150lbs) you don't even know what suspension is!  (More on this later though).
 

DON'T BE A BONE HEAD ON BREAK IN

Changed the oil and filter every 100 miles for the first 500 miles during break in.  Never stayed at a constant speed more than a few seconds.  Never lugged or chugged and never wound.   Lot of different theories on break in.  Have someone explain a few and then listen to your heart.

Always heated it all the way up and then cooled it off working to longer and longer intervals.  One thing is for sure.   Bikes do break in much faster than they did many years ago.  You're definitely fully broken in within 500 miles, I feel.  With 250 miles I was tapping all the power it had to offer (which wasn;t much).

I do know other people who've taken brand new XR's and ridden them hard from the first day and gone up to 500 miles before their first oil change and that's fine, for them.  But when they get done riding my XR I feel sorry and they feel stupid.
 

KILL THAT O-RING CHAIN!

This is one that a lot of people flip out on.  In my personal opinion the day you get your brand new XR you should immediately KILL or TRADE IN that O-RING CHAIN!  There are 2 reasons and I can show you how to substantiate both of them!

1)  The O-RING chain robs power and unless you're riding a 600 I want every ounce of power I have coming to me!  To prove this (provided your sprockets aren't worn out) replace your O-RING chain with a standard chain and ride up a mountain road on the street and feel how your bike pulls.  If you don't feel a power difference you'll be the first to prove me wrong.   A guy once told me "If you can feel it, it's at least a horsepower in gain" and I believe him.

2) O-RING chains wear out faster.   Notice I didn't say stretch out faster?!  The O-RING chain is made for the street and I'll show you how to prove it.  Yeah, I've heard it before "The O-Ring chain is designed for dirt, to be sealed and keep the elements out".  In theory that sounds great, but in reality it doesn't work!  Take any XR on a stand and spin the back wheel paying close attention to the resistance.  Take that same bike and slap a standard chain on and repeat the process.  You'll find that the standard chain spins 500% more freely.

The problem with the O-RING chain is that once ANY water gets inside the chain past the o-rings (this will happen in 15 seconds if you use a garden hose on your bike!) it will begin to rust and rust expands.  This causes an incredible binding to take place.   Prove it to yourself right now.  If your bike is even a 3 months old take your chain off and examine the links.  You'll find you have some links that are frozen and very difficult to move with your hands.  I've seen links so frozen they could only be moved by putting the chain in a vice and beating on it with a hammer!!!  Every time you see an XR pay close attention to the chain and you'll  commonly see FROZEN LINKS.  These links rob power and torque.
 

BUT THE O-RING CHAIN STAYS LUBED LONGER, STRETCHES LESS AND IS QUIETER!

Unless you only lube your chain once a month, an O-Ring chain might be better for you.  I lube my chain every ride.  It is a tad quieter but who can hear the difference with a helmet and exhaust anyway?  As far as the stretching part I think I can disprove that one now too!
 

NOT ALL CHAINS ARE CREATED EQUAL!

In the past I will admit that the one drawback to the standard chain is that it needed to be adjusted every other ride.  Now I've found away around this.  A friend of mine used to ride a CR500 and went through chains like most people go through rear tires (avid hill climber).  Finally, he turned me on to the chain he discovered that could withstand his abuse.  That's the chain I put on my XR.  That chain is an...
 

ERT GOLD SERIES CHAIN

Don't run anything else!  It will stretch a little the first ride but then will stretch no more than an O-Ring chain.  For a guy like myself that has sworn by standard chains on XR's for years it is impressive to see!!!

After every ride clean your chain with a stiff wire brush, getting all the grime off and then hit it with lube.  I've tried a lot of different stuff but the one I like best is the red stuff:

SILKOLENE PRO CHAIN LUBE

Every once and a while you may opt to clean your chain in a solvent tank and then soak it in gear oil.
 

UPDATE ON O-RING CHAINS!!!

The one expception to o-rings chains is if you live back east and ride in the mud a lot.  In this case the o-ring chain may be better suited.  Especially if you do a lot of long rides.