Here's a writeup I did for cagarmy a while ago, on how to change out your front pinion. 1. Why should I consider changing the pinion?
More top speed! Depending on what rear sprocket you're running, going up from a 6 tooth to a 7 tooth pinion (while keeping the rear a 68 tooth), will increase your top speed approx. 4-5 mph. But there is a catch (isn't there always a catch??)...you will lose a bit of your bottom end, therefore coming out of the corners will be pretty slow compared to a 6 tooth running the same rear sprocket.
If you're running on a long track, a 7 tooth will be beneficial on the straights, since your top end will be higher.
If you need further information on how your speed is affected by changing the front or rear sprocket, go to:
www.minimotogarage.com
This speed calculator is a great way to mess around with sprocket combinations to see what you want to experiment with.
2. Is it easy to change my 6 tooth to a 7 tooth pinion? YES!
Here are the list of tools/items I used to take change out my pinion.
A. Gator Grip (can be purchased at Wal Mart for approx. $14.00. It may be cheaper at other stores). It comes with its own Socket Wrench
B. Vise Grips
C. Snap ring pliers or needle nose pliers
D. Allen wrench to take off clutch bell/drum from the bike.
E. Towel
F. Loctite Blue for the pinion
First, take off the clutch drum from the engine. There are 4 bolts holding the drum to the engine. Don't worry about taking off the rear tire to take off the chaing. Taking off the 4 bolts that hold the drum with loosen the chain and will come off easily. Once the drum is off, place the drum on a bench. Take your towel and put it on the outer and inner housing. I did this because I didnt want the Vise Grips to chew up the inside of the clutch drum. Attach the Vise Grips over the towel and make sure it has a firm grip on the drum, to where it won't spin.
Take your snap ring pliers or needle nose pliers and take off the C Clip thats attached to the drum. Place it where you know you won't lose it.
Now take your Gator Grip socket and place it on the pinion. The Gator Grip forms to the shape of the pinion, where it will grab the pinion good. Now if this is the first time you've attempted to change out the pinion, one thing to know is that its on there pretty good. The factory placed some thread locker on the pinion threads so it will stay in place.
Once you know the Gator Grip socket is on the pinion good, turn the socket wrench with the Gator Grip counter clockwise, making sure the drum doesnt turn (that's why the vise grips are on). If its on there good, don't give up, it'll turn eventually. Once you break through the thread locker material, it will loosen easily.
Once its off, take some Loctite blue and coat the 7 tooth pinion threads. Now screw it on to the drum tight with the Gator Grip. Place the C Clip on. You're almost finished!
Line up the chain to the rear and front sprocket, bolt on the drum back to the engine with the 4 bolts, and you're finished! Pretty easy huh?
Spin the rear tire by hand and make sure the rear and front sprockets are lined up well. If it is, test it out.
That's it for now. More tips coming soon.
-Eric
