I ride about 300 to 400 feet above sea level, so any jetting for altitude would have to be compensated for.
I have settled at two jet sizes richer on the main jet, the needle set one notch lean, and one jet size leaner on the pilot jet. I'm getting closer to perfect on the combination with each change I make.
This is with the trail pipe and stock silencer / spark arrestor. A freer flowing silencer would probobly require richer jetting than what I have.
The hunting camp is dryer than a tinder box, so riding without a spark arrestor is not an option.
The figure that I was told on two stroke engines was for every 1500 feet of elevation change, was one jet size. Jet leaner for higher altitude, richer for lower elevations.
As for the tools required, a long #2 phillips is needed to get to the carb mounting clamp, while I use a long 1/4" drive extension with a 5/16" universal socket to get to the airbox clamp and don't have too much trouble.

 

I own a 97 sport 400 and am wondering how much you guys have spent on yours pipe, reeds, clutching, etc. I have mine and the only mod is a K&N. but while im waiting for the cannondale and yamaha quads to come out and the new polaris sport quad in 2001+ is an option if it is lighter. so while i wait im going to try and modify my 400 for some oval dirt track racing but i dont plan on spending over 5-600$$$$ just to hold me over for a while. so will a pipe, rad valve, clutch kit give me the seat of pants and low- upper midrange i need. or is it a must to go all out to get power to the ground. Another ? is what about progressive helixes, roller clutches, etc.? Do they need to be installed in addition to the $150 Clutch kits and what added performance do these bring. By the way back in 98 when i first looked at the stuff on HPD it was all about half the price it is now (clutch kit $79, head mods $75-100) oh well shouldnt have waited so long i guess.