Sprockets

[Spydie]

A couple of weeks ago I put a 13 tooth front sprocket on my little red donkey. I like the lower gearing, it's the same 3.00 sprocket ratio the old CT90's and CT110's had.
But I would rather go up a few teeth on the rear sprocket because small front ones wear fast. When I had the rear wheel off to change the tires I carefully measured the rear sprocket and sat down with a JT sprockets catalog and read till my eyes bled. It payed off and I found a 45 tooth rear and a 15 tooth front sprocket that fit. It's the same size sprockets the old bikes came with . No issues with clearance and I used a new D.I.D heavy duty chain, 112 links.
The bike is much more capable off road with the lower gearing, and doesn't effect the top speed except for a bit higher RPM. There is some speedometer error but I don't care, I will never be breaking any speed limit on this bike. Just my personal opinion, but these sprockets should have been standard.

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Are these the exact same bolt pattern/sprockets that fit the CT110 also? (someone said they are), anything we find that fit a CT110 should work? I'm thinking 14/41 for a 2.93 gear ratio. Just a little more power than the 2.79 stock, but not quite as high of RPM as the 3.00 gearing everyone seems to be going for. If I can find a 41 tooth that fits, or find a 44 tooth and use a 15 on the front for the same 2.93 gearing. That's iff a 41 and/or 44 are available.

 

[Spydie]

After studying https://www.gearingcommander.com/ gearing choices I've decided that 14/41 MIGHT be the best gear combination. While everyone seems to be going for the original 3.00 gearing of the CT90/110 with a 13/39, 14/42, or 15/45, and while that gear ratio does have plenty of power, it also has pretty high revs at road speed. The 14/41 has the least chain wear of any of those other 3.00 gear ratio combinations, or any combination that gives you a 2.93 gear ratio that 14/41 gives you. The 2.93 gear ratio will give a little more power than the stock 14/39 and a little less than the 3.00 combinations, but it will give you only a 328 rpm increase over stock whereas the 3.00 gear ratio raises your rpm at 50 mph by almost 500 rpm. It might be a good compromise, and it might turn out to be the worst of both worlds. Only time will tell. Now I gotta find a 41 tooth rear sprocket.

 

[South of the border]

That was me. Every 10 miles on the highway (without any stopping) the ABS light starts flashing and the ABS quits working (fault light). Opmid, where my new speedometer comes from, said that is expected and you need a speed compensator to overcome that. They'll have one out in May. Off road, no problem because of the occasional rear wheel spin.

Hi Spydie, so what sprocket combination did you put on yours? Was this the cause of the abs light fault? Or something else? You mention Opmid. Did you upgrade the Speedo? This wasn’t the cause?
Reason I ask I’m keen to gear mine down a little but want to be sure I don’t trigger some abs fault. Thanks in advance. Andrew

 

[r80rt]

Are these the exact same bolt pattern/sprockets that fit the CT110 also? (someone said they are), anything we find that fit a CT110 should work? I'm thinking 14/41 for a 2.93 gear ratio. Just a little more power than the 2.79 stock, but not quite as high of RPM as the 3.00 gearing everyone seems to be going for. If I can find a 41 tooth that fits, or find a 44 tooth and use a 15 on the front for the same 2.93 gearing. That's iff a 41 and/or 44 are available.

No, the CT110 sprocket is different. The bolt pattern is right but the bolt hole sizes are too big, the CT125 has 8.5 mm bolt holes and the CT110 uses 10.5 mm.

 

[G19Tony]

I'm glad I'll have a 13T on hand, but I'm going to run it stock for awhile and see how it does. I appreciate you doing all this research. That gearing stuff makes my eyes spin around.

 

[r80rt]

You have to find what works for your needs, there is no one perfect gear ratio for everyone. 3.00 ratio works well for me, you may need something higher or lower, it all depends on where you are, what you are doing and how you ride. That being said, I had no problem doing what I wanted with the stock gearing, but for me, lower is better.

 

[m in sc]

agreed. and typically the gearing wont affect the abs. anything over what it perceives is what, 12? mph it goes out. again, saw this in the grom world a lot (gearing changes) and it never affected the abs.

that being said...

I have a cam coming for the trail. its a TB cam that should be a drop in and go. (like 70 bucks new) I plan on NO other engine changes and the stock ecm should compensate for it fine if thats all i do. the motor will hit a wall at 7000 rpm due to stock cam, again, learned this from the grom world. this should help with what most are trying to achieve with the gearing. I'll report back when it arrives and installed (should be this week). as long as the intake and exhaust stay stock should be a drop in and go and give AT LEAST 500-600 rpm more power curve. Pretty sure factory redline is 8200-8500 stock. This should help use a bit more of that, and leave gearing stock. Just something to think about. .02

 

[Spydie]

No, the CT110 sprocket is different. The bolt pattern is right but the bolt hole sizes are too big, the CT125 has 8.2 mm bolt holes and the CT110 uses 10 mm.

Thanks. Now I have to ask you how your found that one with 8 holes in it (8mm and 10mm I assume?)? Did you have to contact JT directly? I want one just like it but 41 tooth.

 

[Spydie]

agreed. and typically the gearing wont affect the abs. anything over what it perceives is what, 12? mph it goes out. again, saw this in the grom world a lot (gearing changes) and it never affected the abs.

that being said...

I have a cam coming for the trail. its a TB cam that should be a drop in and go. (like 70 bucks new) I plan on NO other engine changes and the stock ecm should compensate for it fine if thats all i do. the motor will hit a wall at 7000 rpm due to stock cam, again, learned this from the grom world. this should help with what most are trying to achieve with the gearing. I'll report back when it arrives and installed (should be this week). as long as the intake and exhaust stay stock should be a drop in and go and give AT LEAST 500-600 rpm more power curve. Pretty sure factory redline is 8200-8500 stock. This should help use a bit more of that, and leave gearing stock. Just something to think about. .02

Every 10 miles my ABS fault light comes on when highway riding with a 13t front sprocket. Opmid, makers of my new speedometer, says that is normal for that much change in gearing (one tooth on the front). When off-road riding, I think the rear wheel spins a little and the fault doesn't come on (yet).

 

[Spydie]

Hi Spydie, so what sprocket combination did you put on yours? Was this the cause of the abs light fault? Or something else? You mention Opmid. Did you upgrade the Speedo? This wasn’t the cause?
Reason I ask I’m keen to gear mine down a little but want to be sure I don’t trigger some abs fault. Thanks in advance. Andrew

I put a 13t on the front. The ABS fault came on every 10 miles of highway riding with my factory speedometer. In my new speedometer I can turn off the light, but the fault is still there and the ABS isn't working until I restart the bike. Opmid, the makers of my new speedometer, said that is normal with a 1 tooth gear change. doesn't seem to happen off-road maybe because the rear tire spins a little? The only way to fix it is with a "speed compensator" but so far I don't think anyone is making one for this bike. It has a weird connector, just like the headlight has a very proprietary connector also. Watch my video at:

 

[r80rt]

Thanks. Now I have to ask you how your found that one with 8 holes in it (8mm and 10mm I assume?)? Did you have to contact JT directly? I want one just like it but 41 tooth.

I sat down with a JT sprockets catalog and compared sprockets till I found what I was looking for. I had to order it from England, I couldn't find one in the USA. The 41 tooth JTR269-41 is available on Ebay.

 

[m in sc]

I linked to one in another thread i think. 12 o clock labs has one that you can wire in.. to basically anything. modifies the signal from the sensor. Get the general one, its like 3 4 wires. have you put the 14 back on and it goes away?

 

[Spydie]

I linked to one in another thread i think. 12 o clock labs has one that you can wire in.. to basically anything. modifies the signal from the sensor. Get the general one, its like 3 4 wires. have you put the 14 back on and it goes away?

Yes, it does. Works fine with the 14t. I don't want to cut wires and wire one in. I want one designed for this bike. But thanks for the heads-up. Opmid is releasing one in March. I am in touch with them. they aren't sure if they'll ship it to the US, though.

 

[m in sc]

I hear ya. thats crazy its that sensitive.

 

[Spydie]

I sat down with a JT sprockets catalog and compared sprockets till I found what I was looking for. I had to order it from England, I couldn't find one in the USA. The JTR269-41 is available on Ebay.

Thanks. The shipping from UK really kills you, but I'm going to have to order it anyway. That one fits a lot of different bikes, Honda CG125 Brazil 1985-92, Kymco 125 hipster 2001-04, Honda MSX125 2015, Mash Seventy 125 2016, Honda ST90 1971-75, Honda SL, Honda XL, Honda TL and whole bunch of others. Not one mentions the CT125. Hope it fits. It will cost too much to send it back. Hey, I just found Amazon has the 45t for $25, free shipping and easy returns, but not the 41t.

I sat down with a JT sprockets catalog and compared sprockets till I found what I was looking for. I had to order it from England, I couldn't find one in the USA. The 41 tooth JTR269-41 is available on Ebay.

I just talked to the Georgia plant for the JT sprockets. A woman answered the phone and she was the rudest person in the world. She told me they don't make a sprocket that will fit our bikes. I told her about your sprocket and she assured me that it is not matched properly, not mounted properly and it will damage your bike and it will void the warranty on the bike. I asked her if they had tried it on our CT bikes and she said she didn't know. I told her that the only reason they don't have it listed as fitting our bikes is because they have never seen nor had their hands on a CT125 yet so they really don't know what they are talking about. But I told her my real question was, all the JT sprockets on Ebay come from the UK (and she butted in and said "no they don't"... so I told her I had looked at every one of them and they were all from the UK. She said we don't sell to the public. I said I know that, but dealers for your sprocket sell on Ebay and Amazon). Man she was rude. If I order a 45t like yours on Amazon, the picture looks like yours, but if I order a 44 (then I have to buy a 15t front sprocket in order to get my 2.93 ratio) the pictures of all the other sprockets at that dealer have 6 holes, all the same size, instead of the 8 holes like yours. She said those are probably stock pictures because the JTR269 all have the eight holes. So I'm going to order one today. Not sure if I'll get the 44t and the 15t from Amazon, or order from the UK for a 41t and wait until sometime in March to get it (shipping is really slow from UK as you already know). Thanks for your help. But you are sure there is no mis-match? It fits perfect just like the factory one, right? Thanks again.

 

[r80rt]

I went through all that nonsense with JT sprockets too. I have the JTR269-45 tooth on my bike, it fits and works as it should. I recommend nothing, I'm just saying what I did on my bike.

 

[m in sc]

reach out to hard racing or mmntbx they carry the grom sprockets, i cant imagine these are any different. heck, i prob have some laying around i'll never need.


as an fyi, if you 'upgrade' to a 520 chain, the honda rebel 250 (up to 2012) rear sprocket is a direct bolt on.

But, here's another option:

HONDA MSX 125 GROM Chain Kit - SUPERLITE Steel Sprockets with Choice of Chain - SprocketCenter.com

Lightweight steel sprocket kit from Superlite Sprockets for the Honda GROM. All kits are offered with multiple gearing options and chains cut to length making installation quick and easy!Each Superlite sprocket kit comes with the following parts-(1)

sprocketcenter.com

 

[r80rt]

A Grom sprocket should bolt on, but it uses a 420 chain pitch, The CT uses 428.

 

[m in sc]

they sell 428 conversion sprockets. common mod on the grom making HP. When i had the 4V head on mine was pushing almost 30 HP, would eat a 420. those guys carry them.. but also:

DID Gold Heavy Duty 428 Chain & JT Sprocket Upgrade Kit Honda MSX125 Grom 13-20 | eBay

428 Upgrade D.I.D Chain & JT Sprocket Kit For Honda MSX125 Grom. As Standard The MSX125 Runs A 420 Chain This Upgrade Kit Is To A 428 Chain Which Is A Lot Stronger And Thicker Which Gives Improved Looks On The Bike Whilst Giving A Lot More Mileage From The Chain.

www.ebay.com

 

[Spydie]

I went through all that nonsense with JT sprockets too. I have the JTR269-45 tooth on my bike, it fits and works as it should. I promote and recommend nothing, I'm just saying what I did on my bike.

Thank you my friend. You have been a big help. It will cost me about $45 plus tax from UK for a 41 tooth. Or I can get a 15t front and 44 rear for the same 2.93 ratio from Amazon for $39 plus tax and get it a lot faster. Rear sprocket by feb 12 and front by feb 17-18 and easy returns if anything doesn't work right. But the 15/44 has a lot more chain and sprocket wear than the 14/41, with 15/45 being the absolute worst you could get for a chain and sprocket wear. According to Gearcommander.com

reach out to hard racing or mmntbx they carry the grom sprockets, i cant imagine these are any different. heck, i prob have some laying around i'll never need.


as an fyi, if you 'upgrade' to a 520 chain, the honda rebel 250 (up to 2012) rear sprocket is a direct bolt on.

But, here's another option:

HONDA MSX 125 GROM Chain Kit - SUPERLITE Steel Sprockets with Choice of Chain - SprocketCenter.com

Lightweight steel sprocket kit from Superlite Sprockets for the Honda GROM. All kits are offered with multiple gearing options and chains cut to length making installation quick and easy!Each Superlite sprocket kit comes with the following parts-(1)

sprocketcenter.com

Grom is a 420 chain. We need a 428, so no, Grom and Monkey sprockets won't work. I checked that sprocket center place and they don't have anything in a 41 tooth 428 chain. But thanks anyway. I'll check Hard racing now. that's where I got my Opmid speedometer from. Nope, hard racing doesn't have any JTR269 products at all. I just ordered one from the UK for $26 shipped. Will supposedly be here by March 1 but with covid I'll be lucky if it's here by May.