Woods gearing--yz 125--how many teeth to add?

I've been putting a lot of hours on my YZ 125 in the woods, and I must say that I been pleasantly surprised at the durability of the stock chain/sprocket set.  Whenever is does succumb however, I'll need to gear down, as the stock gearing seems a little tall.  What do you guys like to run in woods, and will there be any issues with larger rear sprockets interfering with the chain guide?

I've been putting a lot of hours on my YZ 125 in the woods, and I must say that I been pleasantly surprised at the durability of the stock chain/sprocket set.  Whenever is does succumb however, I'll need to gear down, as the stock gearing seems a little tall.  What do you guys like to run in woods, and will there be any issues with larger rear sprockets interfering with the chain guide?

 

You will need a longer than stock chain for every tooth bigger

13/50 has worked well for me doing half woods half MX, however if you are doing strictly trails 13/51 may be better.

I love the low end grunt for my bikes in the woods. I am the only person I know of to run a 13/53 or a 13/54 depending on track. I love to lean it far over in the sand berms of Texas in the woods and know it will come back.

GoYamaha

Sorry to hijack a bit but im wondering the same thing. I ride my 05 yz in the woods almost entirely with 13/48 gearing since the trails i hit dont get too technical. Im about due for some new sprockets and chain and i was thinking about bumping up a tooth on the rear. Will this make a lot of difference or will i have to jump up two or more teeth to get a noticable difference? 13/53 seems like itd be super low gearing

 I run 13/51 on a YZ144 for tight woods, it works good but next time I will go 13/50.

I raced harescrambles on my stock YZ125 in some hilly areas, ran 13/50 without a problem as long as you are halfway aggressive on hills, worked well for the occasional trips to the moto track too.

Well actually I'm going to stick with the stock gearing. I was doing some testing with timed sections, and I was really surprised that screaming it out in first gear on single track trails like we encounter in our race series resulted in substantially faster lap times. It was surprising because shorter gearing in second gear with lots of clutch abuse feels a lot faster, but the stop watch does not lie. Although it feels really jerky and takes getting used to, I am consistently faster revving it silly in 1st gear with standard gearing.

So 13/49 perfect middle ground? Haha guess I'll just give it a shot and see since the common theme is adding teeth on these yz's

running 13 49 for semi tech, i had a 52 rear on and the gearing was way too short.

It's not hard to test different final drive ratios without spending a lot of money.  For example, if you are still running your stock gearing and the chain has got some stretch to it, just buy a cheap steel 49 and compare your lap times.  Another option is to buy a longer chain than you think you need along with some bigger rear sprockets, and cut the chain as needed.  I always have some old chains laying around of different lengths, and I just mix and match with cheap sprockets to try things out.  The important thing is to go by what the stop watch says and not how fast it "feels".  In keeping track of results for both my son's racing activities and my own, I have found that it is not unusual at all for "feel" to give a very different impression than actual lap times.  The stop watch should guide your work.

I run 12/48 or 12/47.

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