I get endless emails about sprocket size questions, so I decided to try to explain the sprocket size choices and a few combinations to help riders understand what the different front and rear sprocket sizes do. If you have input, drop it in the comments below. Gearing for the honda crf 50 and xr 50 comes down to what engine size, riding type, and personal preference. I will cover a few cases in this article.
First let me explain what the different sizes of the front sprocket, known as the countershaft sprocket do. The stock size is 14T and going up or down from this stock size will change the way your bike accelerates, but does not increase your horsepower. If you go to a 13T in the front, you will loose top speed, but it will make the front wheel come up a little easier with the stock 50cc engine. If you go up to 15T, 16T it will increase y
our top speed, but will make the front wheel harder to crack up with the stock 50cc engine.
The second option to change gear ratios is the rear sprocket. The honda CRF 50 comes with a 37T. www.50stunt.com makes sprocket sizes of 30, 34, 37, 40, and a massive 45T. the same principles apply to the rear sprocket, but the opposite results. Incresing the tooth count on the rear sprocket will lower the top speed, and help the front wheel pop up with the stock engine. This is the opposite of the front sprocket.
to summarize, here is what you need to remember
Countershaft Sprocket : Increase tooth count = more top speed
Decrese tooth count = less top speed
Rear Sprocket: Increase tooth count = less top speed
Decrease tooth count= more top speed
Changing 1 tooth on front = the same effect as 3 teeth I’n thr rear
Now that you understand the basics, I can explain my sprocket choices for the crf 50 and xr50. it really comes down to what engine you have, and your riding style.
Stock Engine, 50cc:
A lot of riders like to reduce the top speed giving the engine a feel of having more power by changing the torque applied to the rear wheel. The stock gearing works well for the stock engine in my opinion, but going to a 13T up front, or a 40T in the rear will help get the front wheel up in second gear, making it more usable for straignt line combos. If you yank hard enough you can even get it up in third easier.
Big Bore engine 88cc+
If you upgraded your engine, like I do on every build, you might notice that first gear is almost useless. the increased power and torque just rips right through first. This is the reason I change gearing after insatlling 88cc kits, or 108 kits. I like to increase the top speed by adding teeth to the front, and reducing teeth in the rear. My favorite setup is the stock front, 14T and a 34T rear, sometime I will go up to 15T front if I am railing the track or parking lot minimoto style. But for stunting, the increased top speed makes first gear sweet for circle combos because the bike goes faster in first, and every other gear. for the 108cc I have run 15/30 and cracked over 50 mph, and still had the low end to bust circle combos no problem. If you go to far on the gearing without enough hp, your bike will feel a little sluggish out of the hole, but rip on top, flyin past all your homies.
I hope this artile helps you choose the right gearin for your style, either way. Keep one wheel up!!