Fitting a 17 Tooth Front Sprocket to your CB125E

The standard front sprocket on a CB125E has 15 teeth. A 16 tooth sprocket fits with no problems but a 17 tooth needs just a little work. The sprocket cover plate needs just a little modification to make it fit.
This video assumes you are proficient enough to change your sprocket and tension the chain, it just gives a little help if your wondering how best to tackle the sprocket cover fitment problem.

[@douglasrhine4640]

I have the 16 front on , will try the 17 just to have something to do.. thanks for the upload

[@highoctanecommuting3862]

I found that the 17 tooth front sprocket in combination with the 42 rear was a little too high for someone of my weight on the 175cc motor but I think the featherweights will see an advantage for sure!

[@Chr0nalis]

Thanks for the video. I was also thinking of doing this mod and I came across the problem of the metal protector not fitting. That part is easy to solve, as you just showed. What bothers me though are two things. First of all, with the 17T sprocket the chain no longer touches the rubber chain guide near the sprocket. I cannot find the complete information on what that chain guide does so I can't tell if it's a bad thing. Second negative is that it's more difficult to tell when your chain needs replacing. With the OE configuration, you should replace the chain when it has reached the rearest tensioning point. With a larger sprocket this is no longer true. This isn't that much of an issue though.

[@highoctanecommuting3862]

I wouldn't be too concerned about the guides, they mostly prevent a loose chain from doing damage. I see what your saying about the chain replacement, fair point. I use O-ring chains on everything and I consider them to be good value. Generally when one or both sprockets wear out I replace both sprockets and the chain at the same time. Use a good quality chain lubricant and you will get thousands of kilometres out of them as a set. The sprockets will fail before the chain usually, though the chain will be getting fairly sad by that point anyway.

[@lennythecat7696]

Does the 17T front sprocket make a noticeable difference for freeway speeds? I'm considering getting one, but it'll need to do some freeway commuting.

[@747fa]

Please excuse my ignorance but if you replace the standard15 tooth sprocket with the 17 tooth sprocket the Honda CB125E develops higher speed/s, ie; 100k's/hr or more? Thanks.

[@jeffeeeeeee]

I'm no expert,however I did put a 16 tooth front sprocket on my 125e and noticed a difference through the gears and top end speed. I live out in the bush so much of my riding is on dirt roads and bitumen highways.The bike is now able to sit comfortably on 90Ks instead of revving its guts out at 80 ks prior to the sprocket change.Its top speed is 100ks. I have toyed with the idea of fitting a 17 tooth, however the bike is after all only 125cc and I figured I'd be changing down gears to often even on gentle inclines.My two cents.

[@douglasrhine4640]

100 kms is about all I can manage on the 16 tooth and that’s on flat ground. I weigh about 86 kilos.

[@highoctanecommuting3862]

I guess the trick is to gear it up to the point where it actually gets slower, within reason I suppose. Have you noticed your bike goes up hills better when the tank is empty? :)

[@douglasrhine4640]

High Octane Commuting Lol never thought about that,,,it’s a great little bike.

[@highoctanecommuting3862]

​@@douglasrhine4640 Yep, they are a great little bike, you can tell that I'm a big fan of them too! My CB and I go everywhere. I only use a bigger machine if I'm heading out into the country.

[@chriscs9080]

Never run the bike with empty tank .. you fuel pump eventually will die 👎 all the junk from the bottom of the tank will clog it

[@hankun8614]

Hi mate do u still got the stock for the sprocket and chain? 17T for front and 42T

[@highoctanecommuting3862]

I've checked physical stock and it seems we are retaining a set for our own purposes. I've put these on the website www.highoctanecommuting.com.au/shop/honda-cb125e/55-honda-cb125e-1642-sprocket-set-16-tooth-front-42-tooth-rear.html If you've been watching the news you may have gathered we are having increasing supply problems :(

[@ryant4681]

Do you have a workshop?

[@highoctanecommuting3862]

A private one, it has all the conveniences. Garbage bin, grinder, motorcycle... 8-)

[@highoctanecommuting3862]

I should add that if you are going to use a grinder you should take it away from everything, especially your bike. The sparks that fly off are little hot pieces of metal that will melt your into paint and ruin it.... they then rust and finish the job off.

[@ryant4681]

@@highoctanecommuting3862 Good stuff hopefully it has a beer fridge as well! I am looking for someone to do abit of work on my cb 125 let me know if you are interested, I am in sydney by the way

[@highoctanecommuting3862]

@@ryant4681 I generally don't work on other peoples machines sorry. But for my curiosity, whereabouts in Sydney are you (just generally speaking) and what work are you planning to do on your bike?

[@paulgoh7963]

Actually the gear ratio is if you increase front 1 sprocket tooth is equal to behind reduce 3 sprocket tooths . So I had same problem as you 17 sprocket tooth can’t fix in so I reduce behind by 3 sprocket tooth’s so the results is the same.