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Discussion Starter #1
Just wondering what everyone's thoughts are on sprocket size. I've got the 15 tooth on at the moment, and I guess I feel like it's got it's pros and cons. Definitely seems to correct the speedometer and give it a few more mph on the top end. It's not as zippy at the 14 tooth, but then again I feel like the 14 is constantly rev limit pretty quick. Your thoughts?
 

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There is no wrong answer, and it's all personal preference and application... We primarily ride in the mountain curves, Deal's Gap etc, so we prefer slightly lower gearing for the added snap off a corner. Somebody commuting may well go the other direction to keep RPMs down a bit. Sprocket changes are also handy to return to your starting point after a tire size change, such as going to the 140 rear, which effectively gears the bike much taller. Keep in mind changing rears (generically speaking) allows you to alter gearing in steps a 1/3rd the size of changing the front. We sell roughly equal volumes of front and rear sprockets for what that's worth...
 

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Discussion Starter #5
Yea being out here in TX, especially where I am, we have lots of long flat roads, so I'm liking the 15 for my commutes. I did notice i get a bit more chain rub on the plastic sprocket cover with the 15 though. But I'm guessing it's just a trade off lol. Doesn't really bother me other than the noise. Figure it'll go away eventually. I made sure chain tension and alignment were all good and tried a ride up the road with the plastic off and didn't hear anything, so Im positive it's just the chain slightly hitting that plastic.
 

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Yea being out here in TX, especially where I am, we have lots of long flat roads, so I'm liking the 15 for my commutes. I did notice i get a bit more chain rub on the plastic sprocket cover with the 15 though. But I'm guessing it's just a trade off lol. Doesn't really bother me other than the noise. Figure it'll go away eventually. I made sure chain tension and alignment were all good and tried a ride up the road with the plastic off and didn't hear anything, so Im positive it's just the chain slightly hitting that plastic.
If anyone is thinking of going smaller for better off the line acceleration, note that there might be issues going that way.

I tried a 13T on my Grom and had to switch back to the stock 14T immediately because of chain rubbing on the plastic swingarm pad.
I DO have an aftermarket alloy swingarm on my Grom, which may have made things worse....
 

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Discussion Starter #7
If anyone is thinking of going smaller for better off the line acceleration, note that there might be issues going that way.

I tried a 13T on my Grom and had to switch back to the stock 14T immediately because of chain rubbing on the plastic swingarm pad.
I DO have an aftermarket alloy swingarm on my Grom, which may have made things worse....
I took off the plastic cover when I got home today and busted out the trusty file. I thinned out the approx 1/2 in area where it was touching, (there were obvious marks) leaving just enough to keep the rest of the area clean and such and voila! No more chain rub. It was literally like 1/2 a millimeter too thick for the 15t in that spot but all good now. That annoying sound is gone and I'm happy as a clam. Now if my exhaust would just get here..
 

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If anyone is thinking of going smaller for better off the line acceleration, note that there might be issues going that way.

I tried a 13T on my Grom and had to switch back to the stock 14T immediately because of chain rubbing on the plastic swingarm pad.
I DO have an aftermarket alloy swingarm on my Grom, which may have made things worse....
We run a 13. Non-issue.
 

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Sprockets

Today I put a 38 tooth sprocket on my z125.. and now this thing is so much fun..
I could wheelie it in first sitting down before and 2nd standing up but now 2nd gear sit downs are so easy.. and the thing is actually kinda fast lol before it was slow..
I haven't really tried to see what the top speed is yet as I was just popping wheelies around my neighborhood. But I doubt it will go past 55.
I'm gonna get a 13 tooth front sprocket next.
I first ordered my sprocket from England off ebay and it arrived and it did not fit.. the inside diameter of the sprocket was a half inch bigger than stock.. so be careful if your order from there.. we still trying to figure out why.. maybe they have a different bike called a z125 or something.

5th gear sprockets is now going to be making sprockets in all sizes colors and patterns. So hit them up if you need a sprocket of any size.

Now I'm gonna go race my friend on his grom.. he doesn't know about my new sprocket. We raced on Saturday and he has a grom with cam I take and yosh exhaust and my gf rode the z and she smoked him.. and that was all stock z125..
But she did weigh less..
With me on it he beat me by half a bike length and we were both flat out at the end.
So now if I make the race a little bit shorter I'll definitely beat him..
When I get intake and exhaust I'm sure this thing will smoke him.
 

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I've seen them listed couple places
but I think all I've seen are larger counter sprocket, and larger rear


I want smaller rear but so far haven't seen any


try steady garage or mnnthbx
 

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I've seen them listed couple places
but I think all I've seen are larger counter sprocket, and larger rear


I want smaller rear but so far haven't seen any


try steady garage or mnnthbx


I found smaller counter sprockets on steady garage and larger rears.
Mnnthbx has a 15 tooth counter listed but is sold out. I was gonna go for the smaller rear but decided to go bigger in the front.
 

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I need smaller in the rear because of my stretch and longer chain I had to buy
it may not be long enough for a larger counter sprocket as I don't have anymore slack in it
unless I buy a new chain

where going with smaller rear sprocket I can take out the slack in the chain then a lot easier
 

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Finally found a 15 tooth counter sprocket. Ordered one from Dennis Kirk and found one on eBay. Can't wait to get one of them on my wife's z and then I should have the second one by the time my green z comes in
 

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Was this a typo, or did you really put a 38 tooth on the 125?

Yea, those are stock sizes for the KLX110L and fit great. I'll probably be getting one. For now, I only did 13/32 for playing around. I'll get a 38 and a new chain soon.

You can check out the video I just did about those gears and look in the description to see where I got everything.


--Tom
 

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Yea, those are stock sizes for the KLX110L and fit great. I'll probably be getting one. For now, I only did 13/32 for playing around. I'll get a 38 and a new chain soon.

You can check out the video I just did about those gears and look in the description to see where I got everything.

http://www.youtube.com/watch?v=umzqnWUtUl8

--Tom

So, just to confirm, the Z125 takes the same 420 sprockets as the KLX110? Wonder what else crosses over.
 

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JT Racing Sprockets Part Number:

Sprockets highlighted in green should fit the z125 without clearance issues. Others may or may not have clearance issues.

Front Sprockets
11 tooth: JTF1263.11
12 tooth: JTF1263.12
13 tooth: JTF1263.13
14 tooth: JTF1263.14 STOCK
15 tooth: JTF1263.15
16 tooth: JTF1263.16
17 tooth: JTF1263.17

It appears that any front sprocket that fits a 1986 thru 2016 Suzuki RM80 or RM 85 will fit the z125.

Rear Sprockets:

31 Tooth: JTR 838.31
35 Tooth: JTR 838.35
36 Tooth: JTR 838.36
37 Tooth: JTR 838.37
38 Tooth: JTR 838.38
39 Tooth: JTR 838.39
42 Tooth: JTR 838.42
43 Tooth: JTR 838.43 STOCK
45 Tooth: JTR 838.45
49 Tooth: JTR 838.49

The rear sprocket seems to be tougher to find a match for from other bikes. Looks like a rear sprocket from a 1974 thru 1976 Yamaha RD125 will fit.
 
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