After reading through your website I decided I would volunteer the modifications I did on my 6 year old sons 2000 XR100R. The cost of this project was about $10.00 and that was just for new jetting.

Exhaust
When I purchased this bike I test rode it and thought it lacked some power. After we got it home I first removed the stock exhaust and carefully cut off the end of the muffler about ¼" from the exhaust tip. I took care not to damage the spark arrestor core. Next, I pulled out the inners of the muffler, still attached to the muffler end, and removed everything that was left inside the muffler housing. Then I cut the remaining muffler housing approximately 1" before the muffler mounting bracket. I modified the end of the core to fit into the shortened muffler housing and welded all back together. The noise level is very tolerable and gives a mild roar that wont drive the neighbors nuts.

Carburetor
I installed new jets in the carburetor. I bumped the pilot up from #38 to a #40 and the main jet from #100 to approximately #112 to #115 with the needle clip in the middle position.

Airbox
With a hole saw I drilled two 1" holes in the airbox cover making sure the holes were high on the cover to make it harder for water and debris to enter the airbox.

Ignition Advance
I removed the stator cover and pickup coil. There is an arrow on the stator that points in the counterclockwise direction. The idea of this particular mod is to advance the ignition timing approximately 2 to 3mm in the clockwise direction. I got a drill bit the same size as the original holes and carefully slotted the mounting holes in the pickup coil to allow it to be advanced in the clockwise direction.

New-found Power!
The bike now pulls wheelies in second gear! My sons riding ability is just a beginner so I will have to wait until he advances before I remove the head and really boost the horsepower!

Credits: Article written and submitted by Greg Kipp and edited by 4Strokes.com.