yz125 modifications

Unless you already have a new chain and sprocket you should replace them all as a set. For the gearing change I would recommend adding 2 teeth to the rear sprocket over removing one from the front.

As for the exhaust I really do not feel you can go wrong with any of them. Just choose your favorite and go. ;)

I have heard mixed opinions about the V-force reeds. Although the Boyseen seems to be a proven product and easy to install.

Though it is your money, after the gearing I would save all the other things and send off your forks/shock to be revalved for trail riding. This will make you MUCH faster than any motor mods. Remember, it doesn't matter how much motor you have if you can't use it.

R&D does real good on the yz's but its expensive or trackside but their in minnesota. But yes do the suspension because I had a really heavy mod built and the suspension with everything but valving done did not work. can you say rough oh man I had arm pump in 2 laps.

I put a SFB 7 oz flywheel weight on and it made a nice difference in the woods.

What did the Flywheel weight help you with? I personally have not found the point of a FWW on a 125. I have zero problems with stalling on my 125.

I was riding my 125 in enduros and went to a 12 tooth front so I could get up the hills. Really helped the hill climb but is also really sucked when you hit the high speed section and ran out of RPM. I could have really used a 7th gear.....

Be a little careful in your selection of the pipe. On a two stroke the pipe can be "tuned" for different response. If you are going for impressive dyno results the pipe would be tuned for top end, but that probably is not what will make life easier when it comes to climbing hills. Some pipes are tuned for the low end or for a more broad power.

Rod

the flywheel weight does give a 125 more bottom end... it's more like a tractor it'll pull through mud without revving out as easy. The weight kind've acts like a damper on RPM... however I prefer to ride my bike without it. I like to be able to pop in the clutch, hear the motor hit 12k and drop it so i can launch over a stray log etc. Our motocross track is right next to our trails as well so if i head over to the track the Flywheel weight makes it boring.

But, seeing's how I weigh 120 pounds, suspension is a must for me. Gearing, a pipe, and reeds are all options after that... I love the FMF factory fatty and plain old power reeds in my bike, they give the bike tons more bottom and midrange pull and allow it to rev a bit higher. Gearing... I can't remember exactly how many tooth sprocket I have on mine but I think it's 2 teeth larger than stock on the rear... that helps a lot too however when we hit the gravel roads my buddy on his TM300 whips right by :P