The "best bang for the dollar" is a pipe & air filter upgrade. There's many debates on what's the best pipe and what's the best filter upgrade. Below is my thoughts.....
If deep water is a concern, some people take the factory airbox snorkel and replace its small diamater pipe with a larger snorkel pipe. We do trail riding and water is a concern for us. For pictures of our modified "larger pipe" snorkel, surf Pictures 1, 2, 3 & 4 within Press Here
If deep water crossings or splashings isn't a concern, then you can install the K&N Filter, uni-filter or a foam filter. For details on K&N Filter and its benefits, surf: Press Here
Note: Generally speaking, UniFilter and foam filters yeild simular performance gains. Pick the best for your unique riding conditions.
For the best pipe, Gurus will argue for months about which pipe brand is better. With some pipe upgrades, you must upgrade the clutch. With other pipes, clutch upgrades are optional. For pipes, look at Hetrick, WRH Racing, FMF Fatty and custom pipes from BNC Racing. I've heard each make very good pipes - for specific riding conditions.
Since you are doing trail riding and will probably sell you <nobr><nobr><a class="iAs" style="border-bottom:darkgreen 1px solid;text-decoration:underline;color:darkgreen;background-color:transparent;" href="#" onclick="return kwC();" target="_blank" oncontextmenu="return false;" onmouseover="kwE(event,217960);" onmouseout="kwL(event);" onmousemove="kwM(217960);">mini
</nobr></a></nobr> in another year, you probably don't want to invest too much upgrade money. As a suggestion, look at the following upgrades for your unique riding needs:
- Air Filter snorkel pipe mod or complete factory air box replacement.
- Reed upgrade. We use WRH Racing Reed upgrade in our Pred-90 brand and did notice an immediate power gain.
- Add more compression to your engine. Say 145 PSI with squash (this is a poor man's port upgrade). More compression gives you more bottom end without higher engine revs.
- FMF Pipe (or equivelent) is a good choice for the simple "bolt on" type trail machines. I used the word "equivelant" because BNC Racing makes a simular "low RPM power gain" pipe as well. Hetrick Racing, WRH Racing, etc. pipes are tuned more towards the high RPM "racing type" engines.
- With the FMF Pipe (or equivelent), installing a clutch kit is optional. Some people install a clutch kit for "higher rev" take offs. Great for hole shot or up that extra steep hill type riders. With a clutch kit, your engine will rev higher (like driving you car in 4th grear instead of 5 gear) which means your engine will be a little louder. Louder pipe and higher reving engines many drive some of your neighbours and mountain campers crazy. Clutch upgrades with certain brands of pipes allow the engine to be "tuned" for that specific pipe. Thus, even more benefits from the pipe & air filter upgrade combo.
As a suggestion, talk to Dave at BNC Racing, Billy Holt at WRH Racing and Rich at Hetricking racing to inquire what each of them would recommend for your unique "trail riding" conditions. They are the experts in "performance component matching" for every unique riding conditions.
As a final note, you may also want to review the contents within: Press Here
This site contains info about power bands on motocross bikes. Most of its info also applies to quads engine upgrades.
Note: The two gurus I've delt with are Dave from BNC Racing and Billy Holt from WRH Racing. Great "approachable" folks who really know their stuff.
For more details on feedback from FMF Pipe users, surf: Press Here
Hope this helps....