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17 Tooth Sprocket CBF 125
Blog Date - 20 November 2015
At the suggestion of "Tony" who commented on the CB 125 F review (Honda CB 125 F Test Ride Review) I decided to purchase a 17 tooth CBF 125 front sprocket. Why? I do quite a few motorway miles on my diminutive 125 and this means the poor little engine spends far too long screaming away at probably 7, 8 or 9 thousand rpm. I don't know for sure as my CBF 125 is the early model without a rev counter.
JTF 1264-17 if you want to try it for yourself. Should be about a fiver
The standard sprocket size is 16 teeth. 17 teeth will reduce the number of revs at a given speed, good, but correspondingly reduce acceleration, bad. For a king's ransom of £5 a nice company on Fleabay sent me a 17 tooth sprocket. Turns out the sprocket is the standard front sprocket for the CLR 125 City Fly, a bike I once owned which means I should have kept the dam sprocket from it.
Fitting the sprocket is a doddle. Remove sprocket cover - loosen the chain - undo sprocket bolts - remove the old sprocket - fit new sprocket - check the engine/chain guard doesn't foul - fit sprocket cover - adjust chain.
There's just enough clearance betweeen the chain and the guard that protects the engine.
I have in the past "up-geared" several bikes by fitting a larger front sprocket. In general riding you'd barely notice the difference one tooth makes. On the SLR 650 it helped with the ridiculously low first gear, on the Fazer it moved the vibration point from 70 mph to about 77 mph. The CBF 125 however having much less power and smaller sprockets to start with the difference is more noticeable.
Pulling away in first gear now feels more like a big bike. On standard gearing the clutch can be released within moments, the taller gearing means a little more subtlety is required. Of course there is a minuscule drop in acceleration, correspondingly I can hang on to gears longer which probably compensates in the 0-30 times (0-60 is irrelevant on a 125). Curiously the additional clutching required to get started is minimal but still a negative in traffic yet the ability to hold onto a gear longer makes town work more relaxing. The engine seems that bit more compsed and less frenetic.
Somehow the taller gearing makes the bike feel more stable too. Wait - what?? While it seems like such a small change in gearing would make no difference, the transmission feels smoother causing the bike to ride better. This is a boon considering we're heading into winter's slippery roads and challenging conditions. Maybe I've adjusted the chain better? Maybe the old sprocket was worn? I...I don't think so. I suspect it is partially true I also suspect the larger sprocket "holds" the chain better and perhaps the gearing reduces the small engine's natural snatchyness. Maybe I'm talking nonsense.
Motorways? Well...yes...it is a little better...you are waiting for the "but". There's no such thing as a free lunch. 11 bhp is 11 bhp and no matter how you alter the gears you do not gain any power. At 50 - 55 mph the motor is still a very busy little bee although less so than before. I am aware that I am even more susceptible to headwinds and hills now, thankfully 4th gear will easily pull up to 60 mph without threatening instant self-disassembly. Overall for myself it is an improvement.
I'd suggest the 17 tooth sprocket conversion is only suitable for gentlemen like myself whom are not in a rush and would rather relish a calm and relaxing ride as opposed to a frenzied race to the chip shop and back. It certainly will not make the bike any faster unless you have a massive tail wind and a steep hill, in fact generally it will probably be a tad slower. Learners? I'm undecided, the additional clutch work is a negative though the smoother transmission is a positive.
The larger sprocket isn't a magic bullet nor is it for everyone, but I'm liking it so far.
Oh and of course the BIG question - is the fuel consumption any better or worse? I haven't really covered enough miles over a wide variety of rides to be sure yet. So far I'm guessing it's about the same. Less revs but more throttle required you see. I shall report back after some time if someone reminds me.
Reader's Comments
Bob said :-
Standard operation for me on a big bike, the japanese in particular seem to love revving the daylights out of their engines. All my FX/SLR650s are running 1 tooth over on the front sprocket, like you said 40ftlbs will pull it.
On the FX650 I can cruise at 65MPH and 3900 RPM - lovely.
On my little KE100 I ended up gearing it down, by fitting a 1 tooth over rear sprocket, it didn't need much of a change so a tooth off the front would've been too much. I found on standard gearing that the little thing could barely hold 5th gear, any wind or incline and you were down to 4th. Now with the reduced gearing it will hold 5th more readily, albeit at 2-3MPH lower top speed, but overall the bike is faster because I can maintain my slightly reduced cruising speed for much more of the time.
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Cheers Bob. I guess the bike makers, not just the Japanese, use lower gearing to give bikes that extra acceleration then rely on the revvy motors to make up for the top end speeds.
01/01/2000 00:00:00 UTC
Henrik said :-
I am having problems with extremely fuel-consumption on my KLE, like 14.6 Km/L at 90 Km/h, where the consumption should have been in the area 18-22 km/L. So far only the airfilter has been replaced, without any success,..
Obviously I will attack the problem from all angels possible, and see what
improvements is possible. And then a 5L auxiliary rear-tank is in the pipe-line also upping the total tank-capacity from 15-20L. I won't rest until
my action radius is 350-400 km without the need to fill up. Right now its
around 200 km so there is far to go. Changing the sprockets is one of the things to try out, and why I write here
From stock 16/44 sprockets I will try out with 17/38 and see what happens,
rughly estimated that should reduce my RPM from 4500 to 3500 at 90 km/h
I have no idea what such a change in gearing will do, but look forward for
the test, the sprockets are already on my table, still looking for a new 520 Chain, don't know if the test will be during the winter or in the spring
01/01/2000 00:00:00 UTC
Tony said :-
Hi Henrik, regarding your fuel consumption first thing to do is take a look at your spark plug. Should be a light tan colour. If as I suspect for a sudden change in economy it's sooty black then your mixture is to rich. Make sure your choke mechanism isn't sticking on. Hope that helps.
Changing sprocket sizes, personally I would change one at a time and record the difference. Making the engine work under constant load would have the opposite effect of what you're trying to achieve. Good luck chasing those figures.
01/01/2000 00:00:00 UTC
Henrik said :-
Thanks Tony !!! for bringing a sticking choke mechanism to my attention, that one was not on my list yet ;-) Next thing I plan to do is changing
the plugs, but I try to arrange that so I can measure the compression at
the same time, (just got one of those tools), I will inspect and do fotos
of the old plugs obviously, and also I will try to see if I can get a wiew into the back of the caburettors or somehow else inspect if the chocke is working in the span that it is supposed to. If not possible I will have to delay it untill later when the machine is split more up in peaces. Got to get used to all that work. Removing tank and seat just getting to the plugs and filter is sickening, as I am not used to that on the smaller bikes ;-)
Just bought the bike, don't know much of its story, except that its ben imported to DK from UK, but the heavy fuel consumption was a fact also
for the previous owner. Aside from that, the poor tank-capacity, and a very lousy seat,.. I am happy about the KLE500,.. and keep fingers crossed
There is heavy chain-noise ,. but so it is with all KLE500 they say
It starts well, drives well, and there is nothing yet that easy points out
where the trouble is hidden, could be a totally worn out engine, in that case compression will reveal it
01/01/2000 00:00:00 UTC
Ren - The Ed said :-
Hi Tony & Henrik. Since putting the 17 tooth sprocket on the CBF125 I have NOT noticed any improvement in fuel consumption. Logically to travel a certain distance at a certain speed requires a certain amount of energy which means a certain amount of fuel.
Efficiency can be improved by having the engine running at it's most efficient speed - revolutions. All that can be hoped for is that the gearing places the engine at those revs when the motorcycle is at the speed you most often ride at.
I think you are both right - if the KLE is using a lot of fuel, more than expected, then the mixture is the obvious place to start - ie the carburettor. Blocked air filter?
01/01/2000 00:00:00 UTC
jovin morallos said :-
Naghahanap po kasi ako ng sprockets 17 yung size
22/08/2016 20:19:27 UTC
Ren - The Ed said :-
Hi Jovin. In case anyone's wondering according to Google translate Jovin is looking for a 17 tooth sprocket. I can't help you in the Philipines Jovin but if you Google "JTF 1264-17" JT sprockets in the UK can supply them.
22/08/2016 20:35:52 UTC
Dinesh said :-
Sir,
I want a 17 teeth front sprocket for cbr150r. Can u plz tell me where u deliver this product in Delhi India.
06/03/2017 15:53:31 UTC
Ren - The Ed said :-
Sorry Dinesh, we only blog about bikes we don't sell any parts on here.
06/03/2017 16:07:03 UTC
Phil said :-
Hi guys, my lads has alot of play on front sprocket ? Has anyone else got this?.
It seems like either the sprocket needs a washer behind it as there is about a 2mm movement on it.
30/07/2017 17:35:05 UTC
Ren - The Ed said :-
Hi Phil. There should be *some* play. Unlike larger machines the sprocket isn't tightened onto the splines with a big nut and lots of torque. It's merely held in place by the plate. See the second picture above.
While there is play it ought not be excessive. Remove the 2 10mm bolts, the plate and the sprocket. The splines on the shaft ought to be sharply squared as should the corresponding internal splines of the sprocket. If you're seeing rounded edges then some remedial work is required.
Look at the images above and notice the crisp edges on the sprocket.
30/07/2017 21:51:24 UTC
said :-
27/12/2017 11:04:27 UTC
Andy said :-
After riding my cbf125 2016 for first time, which although 27months old, only had 494 miles on it, I found straight away it was far too revvy, I purchased it as a second bike to commute 20 miles each way to work on motorway.
I want to stay ahead of the lorrys travelling at 56-60mph, without having it balls out all the time, So whilst doing some research, I found Rens great blog.
I purchased a 17 tooth front sprocket from JT and fitted it, straight away it was a pleasure to ride, its transformed my little bike, as Ren says around town you can hold gears longer, so 3 and 4th is all you need, but far better is that on the motorway, its been exactly what I needed, its made it cruise 5mph faster, before with factory 16 tooth sprocket, 60mph was revving at 8,200rpm, now with the 17tooth front, 60mph is now 7,600rpm, and the vibration and harsh sound starts at 70, so I can happily stay ahead of the lorrys at between 60 and 65mph without wringing its neck.
Forget looking at exhausts, air filters etc spending hundreds, under a tenner, and doing thd bike a favoud in the process is money very well spent. Absolutely no negatives for me!
Thanks Ren,
A very happy Andy!
10/08/2018 21:13:39 UTC
Ren - The Ed said :-
Goodness me! I've made a suggestion that made someone happy! I must stop doing this, there's nothing worse than happy people.
Only teasing Andy. I'm glad it's working for you. The time you will struggle with the larger front sprocket is uphill or into headwinds. You might find you have to drop a cog more often than you would if you were on the standard gearing. Run with it and see how it goes over the months ahead.
As you say it's a cheap conversion. My model is the early 2009 version that does not have the rev counter. I'm glad you gave me the figures as I've always wondered what revs I was doing.
My CBF125 now has 75,500 miles on the clock, I hope yours gives you years of trouble free mileage. I'd be happy to hear how you get on.
11/08/2018 06:55:24 UTC
said :-
Hi Ren, just quick update,
Just completed my first whole week of commuting on my cbf125 2016, with the now 17 tooth front sprocket, I did 202 miles, of which 95% is motor way, and it used, 6.91litres of juice. Giving a respectable 132.9mpg. I'm still delighted with the mod, have had couple of days of very strong winds, and only had to change down once into fourth, on a hill up from Avonmouth on M5.
I'm astounded yours has covered 70k thats amazing for such a small bike.
Any problems with the dreaded fuel pump saga? I've read at length about it, and have tried researching to see when they finally fixed the fault, if they indeed have done so yet.
Mine is a 2016 so probbaby a 15 build I guess, now has 880miles on it, although almost 2 1/2 years old. So been stored a while. Not anymore!
Regards Andy
20/08/2018 17:45:29 UTC
Ren - The Ed said :-
Cheers for the update Andy (I guess it's Andy...).
Problems with the CBF? Primary drive ring (the one on the clutch basket) cracked early on. Several spark plug CAPS oddly enough. Alternators last 30k, not cheap but easy enough to change. Not much else springs to mind as yet. No fuel pump saga so far.
Change your oil every 2.5k. Check the tappets!!! I'd do them every 2.5k until they're settled, probably around 10k. Then just check them every 5-10k.
20/08/2018 20:22:20 UTC
Kim said :-
Hi! I just bought a brand new Honda CB125F, and upon inspection discovered that my front sprocket i 15 tooth, which differs from your claim of 16 being standard.
Most likely this is due to Norway (where I live) having a regulation on A1 licence, and thus 125 models, stating a max speed of 96kmh (60mph)
I have ordered two new sprockets: A "plus 1 tooth", and a "plus 2 tooth" from Wemoto.
I believed that would give me a 16 and a 17 tooth sprocket, but if 16 is standard, I will be getting a 17 and an 18...
Exciting!
05/02/2019 17:48:11 UTC
Kim said :-
It must be said that I am only after "an extra gear" at the end, giving me a more relaxed engine on the long flats and downhill. If that makes my first gear becoming more like the second, so be it. I have rehearsed releasing in second, an it's really no problem. And as you say, changing sprocket wont give you more power or higher top speed, only "longer" gears when accelerating, and quieter engine at cruise. I'll check back when I've recieved and tested my new sprockets :)
05/02/2019 18:37:17 UTC
Ren - The Ed said :-
Cheers Kim. Having fitted the 17 tooth sprocket as I stated in the post it only just about fits with the standard guard as shown in the images. I'm not sure you'd get an 18 tooth sprocket in there.
After several months with the 17 tooth I decided to go back to the 16. It's better suited for the commuting and town work that my 125 suffers. It's all about personal taste and the kind of riding you're doing. Let us know how you get on and I hope the Norwegian weather is good to you.
06/02/2019 09:10:00 UTC
Kim said :-
What did arrive from Wemoto was in fact 16 and 17 tooth front sprockets. So maybe there is different standard toothcount on my CB125F, and your older CBF125...
Anyway: I just managed to cram the 17 tooth in with maybe half a millimeter to spare! To avoid changing the brand new chain, I had to adjust the rear wheel forward by about a centimeter.
After riding a few weeks on it now (the roads being icy or wet until recently), I'm very pleased with it! When accelerating you reach the red-line to quickly with the original 15 tooth, and you have to shift gears like crazy. It gets a bit better with the 17 tooth. It is also nice to have the opportunity to relax the engine with a much less "revvy" 5th gear when conditions are right.
Bottom line: You can always downshift when you need it whith a 17 tooth fitted, but you can't upshift when you'd wish it with the original 15 tooth fitted...
That's why the 17 tooth stays put on my Honda CB125F! Thanks for showing me how :)
23/04/2019 12:12:40 UTC
Ren - The Ed said :-
15 to 17 teeth! That's a fair old jump. Glad you're liking it Kim, you'll be cruising almost on tickover.
23/04/2019 20:43:41 UTC
nab301 said :-
In reply to Kim my 2019 CB125f also has a 15t sprocket as standard ( I'm based in Ireland so probably a UK spec bike) and found that I could ride everywhere in 5th gear with motorway use restricted by low speed / high revs . I've recently fitted a 16t sprocket and it definitely is an improvement for motorway use when conditions allow.( 90kph with standard gearing was near the redline while now 100kph is possible without abusing the motor. ) Although now I tend to buzz around urban areas in 3rd and 4th gear because in 5th it easily exceeds the local 50kph and 60kph limits ( I wonder would a speeding ticket increase the value of the bike!)
I'm not sure how accurate the rev counter is though , soon after I purchased the bike I noticed the indicated idle speed seemed high , the dealer plugged in his laptop and the indicated idle speed on that was 1500 to 1600rpm which is within spec....
24/12/2019 19:07:39 UTC
Nicholas said :-
Proud Owner of a cbf125 2015 plate.
1st conversion was 17/42.
2st conversion was 17/40. ( from kzr) needed mod .
3rd conversion high windshield.
4rth conversion was 300mm discbrake.
5th conversion was changing the lever for stronger rear brake.
6th conversion put 2 m2a1 ammo box on either side
7th conversion 5th gear indicator.
8th conversion custom made fuel housing ( 2 pieces)from aluminium and higher capacity for better cooling. Also put a pre filter
9th conversion
Full dc power all around.
And many other I can't recall.
Result .
Real feel bike
Repairable fuel pump
Never hit lever for 6th gear lol.
Perfect feel brakes.
Perfect wind protection.
And many more.
20/03/2020 08:32:56 UTC
said :-
20/03/2020 08:34:13 UTC
said :-
20/03/2020 08:35:04 UTC
Nicholas said :-
A unique cbf with major and exclusive mods.
for the fun of it.
Just a mechanic
20/03/2020 08:49:59 UTC
Ren - The Ed¹ said :-
That's a lot of work and love into that bike Nicholas.
Can you explain what you did with the fuel - you mention "housing" and a repairable fuel pump? And do you think the full DC conversion is worth the effort?
21/03/2020 07:57:51 UTC
HCCI said :-
Hello,
I have just bought a new CB125F, a 2021 model.
The front and rear sprockets are compatible with the CBF125 ones but the biggest front sprocket fitting is the 16T variant.
After installing the 16 teeth sprocket, the gearing is still too short. The new CB125F has the shortest gearing i have encountered so far on a 125cc bike, the fisrt gear is close to useless.
Not being possible to fit a front sprocket bigger than 16T, can someone please tell me where to find a rear sprocket with less than 40 teeth?
Thanks
03/01/2021 09:11:28 UTC
Bogger said :-
Go the JT Sprockets website. That should help with sizes, ratios and part numbers.
Bogger
03/01/2021 11:21:51 UTC
nab301 said :-
Had a quick look, the smallest available in JT (JTR1221 part number ) seems to be 42 teeth and Sunstar (1-2061) is 42 (45 is OE on the bike) but sunstar also list a 34 ! you'd probably need a big bore kit or a tiny front sprocket with that one.... Failing that, depending what part of the world you are in I googled Custom sprocket manufacturers (mainly for race applications )and found a few in the UK that will supply from drawings or samples in aluminium for around £70 stg.
Nigel
03/01/2021 12:37:08 UTC
nab301 said :-
Quote "The front and rear sprockets are compatible with the CBF125 ones "
Double checking the JT catalogue the rear sprocket appears to be different (different pcd on the mounting holes) on the CB125f and they don't list for the '21 model yet . I guess with time you could find something similar in a catalogue that may need to be machined but I can't find an online catalogue with a dimensional search facility and a previous contributor to this thread mentioned modifying a KZR sprocket for his CBF125 , I'm guessing it was some sort of pit bike possibly a stomp?
Nigel
03/01/2021 13:16:49 UTC
HCCI said :-
Hello,
Thanks a lot, i was not expecting so many replies to my request.
The CBF125 rear sprocket fits on my 2021 CB125F perfectly fine but it has too many teeth, four more than mine to be precise.
My front sprocket is a 14T and the rear one is a 41T.
I have tried a 16T sprocket already but the engine light turned on during a trip so back to 14T and engine light off.
Apparently the bigger front sprocket is messing with the ecu.
I am going to fit a 15T front sprocket and see if it will not confuse the ecu.
So for the moment, i will not try to fit a smaller rear sprocket.
Thanks
05/01/2021 00:39:47 UTC
HCCI said :-
Hello ,
Just to say i had it wrong.
The number of theeth on the CBF125 rear sprocket is 42 and not 45 as i wrote and it fits.
The previous CB125F rear sprocket is 45 theeth and it does not fit on my bike.
Thanks
05/01/2021 07:54:49 UTC
HCCI said :-
The engine warning light went off by itself and so back to the 16T front sprocket and so far everything seems to be working fine and after 146 km still no warning light. Something else should have been the cause.
The 16T front sprocket gearing is way better than the original one but first gear is still too short almost useless execpt for take off , the second and third gear doing all the work at low speed.
I also own a 2016 CB125F with a 17t front and a 37t rear sprockets and it is perhaps geared a bit too tall but how smooth the ride is compared to the 2021 CB125F.
I have already ordered a 39t rear sprocket for my 2016 CB125F so the first becomes a bit easier on the clutch wich has very poor feedback during take off..
In comparison the 2021 CB125F clutch is better in terms of feeling and the engine is smooth but the first and second gear being too short is annoying.
I still don' t get how it is possible that there is no other option than the 42 t rear sprocket for the CB125F when most other models have so many options to choose from.
Thanks a lot guys and if You find someone selling a 39t or 37t rear sprocket for the CB125F, please let me know.
10/01/2021 19:07:16 UTC
Ren - The Ed¹ said :-
I wonder HCCI - from what I can glean the CB125F has the speedo drive taken from the front wheel. With the higher gearing the computer is getting confused. Lets say if the computer knows that with regular gearing at 50mph it should be doing, I'm guessing, 6,500 rpm. With the higher gearing 50mph may only be 5,500 rpm. So the computer goes "summat's not quite as expected, I'll put on the check engine light".
There will be some leeway but if you exceed that leeway the computer spits its dummy out. The only possible route that comes to mind would be to have the computer reprogrammed which is either not possible on the "simple" CB25F computer or too costly to be worth while.
10/01/2021 19:30:01 UTC
HCCI said :-
Hello,
That was my thinking also but that can not be because there is no sensor of any kind on any of the wheels and after more than 200km already done with the 16T front sprocket, the warning light is still off.
When the light turned on, one of the things i remember was that i had just turned the engine off with the kill switch and immediatly back on soon after and the electric motor or starter needs some time to put the engine in the induction fase first before initiating the starting fase itself .
As a piece of information, the speed is taken from the output shaft and not from one of the wheels of the bike as it is the case on the previous CB125F.
Thanks
13/01/2021 22:30:26 UTC
Ren - The Ed¹ said :-
Aaaah. So a change from the original speedo on the front wheel. Fair enough. Well then the only thing to remember is if the speed is read from the output shaft because you've changed the gearing your speedo will be "out"! I'd be curious how far out, any ideas? Not that speedos are 100% accurate anyhow but with the higher gearing I wouldn't want you to be getting a speeding ticket.
14/01/2021 12:35:44 UTC
HCCI said :-
Hello,
Yes You are right.
The speedometer is indicating a lower speed like it is doing 50 km/h when it is going at 57.
For the distance traveled, for every 100km on the speedometer, the gps indicates around 112.8 km instead.
One more thing worth saying is fuel consumption, I get around the same numbers on both the CB125F, which is a bit disapointing.
16/01/2021 22:58:00 UTC
nab301 said :-
Interesting! does the fuel consumption comparison with the earlier model take the approx 12% error with the changed gearing into account ? It's disappointing if the actual consumption figure is not any better.
Locally, the importer / distributor is now advertising the Super Cub for less than the early model CB125F , and interestingly the fuel consumption is listed as nearer 190mpg (66.7kml) for an engine with minutely different bore and stroke dimensions , slightly less power and slightly more torque. Although the downside is the miniscule petrol tank capacity.
Nigel
17/01/2021 13:30:31 UTC
Ren - The Ed¹ said :-
Gearing is a method to improve fuel economy - but - no matter the revs it still requires a certain amount of energy to move a mass from one place to another. It goes to show how efficient the Honda is to see that even with different gearing no advantage in terms of fuel consumption is gained.
In this case HCCI the gearing choice then comes down to personal preference. If you're happy with the oh-so-slightly lower acceleration but the gain in not screaming the motor at high speed then great.
Totally agree regarding the miniscule petrol tank nab301. Still, the Cub is a lovely machine.
18/01/2021 12:43:09 UTC
HCCI said :-
Hello,
I own a 2016 CB12F and a 2021 CB125F.
On the 2016 model, fuel consumption is around 1,48 l/100Km or 67,6 km/l.
On the 2021 one, figures are around 1,37 l/100 km or 73 Km/l but at a slower pace.
The 2021 numbers are still provisory but they take into account the gps distance and not the speedo.
The fuel tank on the 2021 seems to be even bigger than the one on the 2016 model but not certain yet.
I have ridden both on the same day and on the same route and the final results were 1,49 l/100km for the 2016 model and 1,43 l/100km for the 2021 one. The average speed was about the same on both bikes but i usually tend to ride slower on the new model because of its lower gearing.
What bothers me the most is first being to short. At 4000 rpm with stock gearing, speed is 14 km/h versus 15 i am getting right now but on the 2016 version, first reaches 21 km/h.
The 2016 model´s taller gearing (17t front and 37t rear) suits me better.
At 4000 rpm, in fifth, the speed is 68 km/h versus 57 (gps data) and in first gear the 2016 model still manages to take off on steep inclines but i think the 39t sprocket on the rear would be a bit easier on the clutch.
21/01/2021 20:42:46 UTC
nab301 said :-
Thanks for posting , they're impressive enough fuel consumption figures . My older model CB125F registered in 2019 has achieved a best of approx 46Km per Litre, but it is generally lower than this. I must check the speedo for accuracy .
Nigel
21/01/2021 21:00:15 UTC
Joe Crennan said :-
I have 3 cbfs 2013 2011 and 2021
Had anyone found a way for getting a rpm reading out of Honda’s computer?
At 9300rpm I have worked out speeds (not gps) 20mph, 37,54,63,74 (I fitted a digital tach temporally)
Top is 73mph on the others
Also how accurate id Honda’s mpg readout?
I am getting 169mpg ave and 240mpg when I tried vs max 157mpg on others and 100 to 120mpg usually (driving hard as I am used to litre bikes).
I have so many bikes I don't do enough to fill a tank and calculate
31/08/2022 18:13:27 UTC
Milan said :-
I've been experimenting a bit with sprocket sizes on a 2021 cb125f; here are my observations:
14t (stock)
+ good economy
- true speed 6% lower than indicated
- vibrations and engine noise are getting a bit annoying at 90km/h (96 indicated)
- 1st gear is too short, I often launch in 2nd.
15t:
+ Speedometer spot on. Less noise at 90km/h, ideal if you spend a lot of time on the motorway drafting trucks (from a safe, 2-second distance, mind you).
- Looks like a little bit more fuel is being used (compensated reading), probably due to not having the most efficient cruising gear available on the flats anymore.
- A bit of difficulty pulling 5th gear otherwise; use 4th when accelerating/slight uphill, 5th downhill. 1st gear a bit more useful than stock.
16t:
+ 4th gear now matches standard 5th gear, similar efficiency should therefore be available, while 5th gear is now only really useful downhill or when drafting.
+ 1st gear is very nice, starting in 2nd no longer useful nor possible.
- Careful with speed limits, as true speed is now almost 7% higher than indicated.
I guess I'll switch back to stock for a while and see whether the efficiency difference between 14t and 15t is real, or my driving style has evolved.
31/10/2022 03:34:34 UTC
Ren - The Ed¹ said :-
Wow! That's like proper research and information Milan, thank you. While I too have experimented with sprocket sizes I do find ultimately the manufacturers tend to know what they're doing. A change in sprocket size is new and interesting and it may fix a gripe that's been niggling... only to find it brings up a new gripe. Gearing is a compromise like most things in life.
Unless - you have a particular and specific need. For example if you ride a lot of motorway on a small capacity motorcycle a taller gearing may help reduce that buzzing engine noise. The compromise will of course be slower acceleration and having to drop a gear into headwinds and/or uphill.
I'll be interested to hear which sprocket you eventually settle on.
31/10/2022 09:02:31 UTC
Marcos said :-
Thank you for the information ,from 15/45 now 17/45 made a massive difference, rev way lower now , and 1st gear is longer and it feels like I have a new bike CBF125 2019
JTF1264 Front Drive Motorcycle Sprocket 17 Teeth (JTF 1264.17) was a tight fit mm to spare
Happy that I changed
Thanks again
30/04/2023 18:44:17 UTC
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