Re: Honda CBR 250R

Niceeee. . 100 % match for the tri-color. ..

Dude what's that tint ?? Smoked or reflective vinyl... looking good boss..

Sent from my GT-I9300 using Tapatalk 2

Re: Honda CBR 250R

Thanks buddy...its a clear glass. no tint.

Re: Honda CBR 250R

Hi Sid, I think Aman is asking about Bike's visor. It is looking good.

Re: Honda CBR 250R

I have wanted lower RsPM at cruising speeds ever since I bought my bike in May 2011.

The most popular (and convenient) way of going about it is to change the front/ rear sprocket. However, the catch is that the speed vs RPM relationship will be disturbed for all gears. Meaning, 6th will yield a lowered RPM for sure but so will 1st, impacting the tractability of the bike from a stationery state.

I have been pondering a new 6th gear wheel so that it yields about 4 odd thou RPM at 100+. Very tentative figures, will be revised once I am able to get some modeling software geek in the auto industry to work on this in return for pizzas and beer

Here is an exploded view of the tranny.

Honda Motorcycle Parts 2012 CBR250R AC TRANSMISSION Diagram

From the above diagram, Part Nos 17 and 19 (gear main shaft sixth and gear counter shaft sixth) will need to be fabricated anew. This will be a delicate job, what with the cutting and splining.

The main shaft gear is 27T while that of the counter shaft is 26T. Either both of one of them would need to be increased by one or two teeth to get the resultant higher gearing ONLY in sixth.

From the diagram, it is not very clear as to which of the shafts provides drive to the front sprocket...

Comments most welcome.

Re: Honda CBR 250R

@icemang sir, the the 6th is already in overdrive, meaning, the pulling power is very less and it's purely for cruising only. Further overgearing the ratios would mean you'd need to redline it in the 5th gear to reach ~115-120 and then drop to ~5000RPM the ultra-tall 6th gear at 110kph+ - with a very significant drop in power and pull. This will be certainly more disconcerting and mismatching the overall riding stance. Moreover, getting the cogs done would be a very minute and precise job which (most) local forgeries won't be able to achieve.

I may be mistaken here, do correct me if I am wrong.

Re: Honda CBR 250R

You are abso bang-on about the kind of precision needed being out of the abilities of local "forgers".

I shall check the RPM vs speed relationship more accurately in a couple of days and then, we can discuss this.

Prima facie, I know my project is doomed to be a non-starter unless I can get the services of a CAM lathe equipped workshop.

Re: Honda CBR 250R

I welcome your curious and inquisitive nature but I have to say it'll cost you a bomb if you want to change the gears (get it manufactured with different number of teeth). Front/Rear sprocket change is the only option. And I'll give you my reasons.
I am a mechanical engineer and I have worked in automobile industry for close to three years now. I have personally seen manufacture and assembly of power-trains (engine + transmission) and production of gears. Gear manufacturing is a very tedious process and setting up a new production line for a new product line costs in crores (at least). Even if HMSI itself wanted to change gear ratios, it has go through a very lengthy and laborious process of on paper design feasibility approvals and thousands of kilometers of actual testing. That is the reason, we very rarely see any all new products; rarely do we get significant power-train upgrades; just cosmetic updates every now and then (true for anything mechanical; cars, bikes, trucks, etc.). As a mechanical engineer, and not as Honda's mouthpiece; what I would like to say is that what you have between your legs is a highly accomplished, tried and tested product.

I'll give you an example:
HMSI launched Stunner 2 years after Shine. The only difference in power-train of Stunner and Shine is an extra gear and high lift cam.

Re: Honda CBR 250R

Cost apart, there will always be the issue of incorrect speedo readings

Re: Honda CBR 250R

icemang, do you feel the bike is stressed in 6th gear..??

Re: Honda CBR 250R

Yes sir thats a C/F Akra,also the dot was not nail thankfully.

----consecutive posts auto-merged-----

Let the bike do 2/3 k kms & then start checking for the shortcomings,gears on bike are forged,hardened pieces of metal they will take time & hard running to get set.So complete your running in & then start giving it a heavy right hand gradually.Even after doing 2/3 k kms if you feel that the particular gear is giving trouble mention it to the ASC.Also just mention it everytime you take the bike to ASC,get it written on the job card,let the mech say whatever he wants get it written on the job card if you are thinking that the gear is troublesome.

----consecutive posts auto-merged-----


The front PSD is 110/70/17 which was shipped from Ahmadabad by a dear friend.Rear PSD is 130/80/17,the bike feels much more flickable than std size rears.Due to the LBT strike here have not installed the front yet.Will post the experience here ones I complete 800/1000 kms with it.

----consecutive posts auto-merged-----

Dear sir pls try a 15t front sprocket in the first place,give it a try first ,see if you like the feel of 6th gear,a friend has fabricated it Chennai along with a 13t front.I myself is using the 13t front as I mostly ride it in Pune city`s chaotic traffic & hardly do any ride more than 200 kms & going by the feel of 13t which lowered the gearing by 7% the 15t will increase the gearing by 7% which I think the CBR should be able to pull in lower gears.On highways it will be relaxed commute but in dense traffic conditions lot of gear changes will be necessery,also with 15t the fuel consumption figures should improve & the speedo will show 7% less speed.Before opening the engine or fabricating any gear give it a try.

Pls feel free to PM me if you cannot locate 15t front as it having 11 splines & not produced by any CO.

Re: Honda CBR 250R

Again, correct there because a @#$%^&* rat had chewed thru the speedo cable a year ago and it had costed me 2200 bucks to replace 'cause it is a tiddly sensor based gizmo taking its feed from the crankshaft.

Prince, woh baat nahi hai. The engine may be perfectly happy doing 7K at about 102 or so. I have been riding bikes and driving cars for 31 years now. I am extremely sensitive to engine sounds and tailor my riding style according to what the engine-gearbox combo speaks to me about. In the CBR, I just know when the engine is begging for a higher RATIO in 6th or a higher gear after 6th. I have flipped my toe upwards so many times on the highway only to find that the gearbox is already in 6th. I just know that it wants a higher 7th with a 0.91 or 0.88 ratio.

That is wonderfully nice of you, Prithvi. One request from you. Is anybody using the 15T front? If so, can you find out as to what is the RPM between 90 and 110? Actually, I am a bit pissed-off by the extremely low 1st also. I guess this fetish for low RsPM comes from my love for diesel engines. Waiting and waiting for the Scimitar to launch...

Re: Honda CBR 250R

With my 3 years of industry experience and your 30 years of actual driving experience; I must say, and with all due respect; I am a 'Rookie' and you, 'Rusted'.

As far as calculation of engine rpm in different gears for a particular speed is concerned, I have calculated all those values for CBR250R and they are posted here. I've also posted a simplified formula for calculation. You can find the same online here.
If you change the front sprocket, secondary/final reduction will change (38/14 to 38/15) resulting in a jump in kmph/1000rpm values (from 16.141 to 17.292 for 6th gear; i.e. @ 5k rpm speed will be 80.70 kmph and 86.46 kmph respectively). But at the same time, I must say that you'll have to live with lesser acceleration and more downshifts within the city limits, though better cruising ability on highways and a small increase in FE.

From your post, and from your affinity for diesel engines, I deduce that you like relaxed cruising. Then you must also like attitude of HH Karizma, and Bullets which are apt for cruising. I would also suggest you to ride a Suzuki's 150cc offering GS150R, which is the only 6 speed bike in its segment. Its 6th gear is essentially for cruising only. Just for the sake of it, a Honda VFR1200F has kmph/1000rpm values as 9.89, 14.81, 18.87, 22.18, 24.93, 27.40 for successive gears. Imagine VFR doing 110 kmph @ 4000rpm in 6th gear!

Re: Honda CBR 250R

Yeah bro...i got that he is asking about the visor tint. Thats what I replied, it not tinted its clear visor.

Re: Honda CBR 250R

the projects can be a real good deal...however as everyone stated that forging in india wudn't be a possibilty .. even if it was.. it will cost a bomb..

keeping all that aside.. you cant take that gearbox and use is in real time... if something goes wrong.. you know whats gon na happen if the gears choke at 100 kmph..


coming from advrider and cbr250.net.. i would suggest go for front teeth increase +1

get a 15T sproket and at 100kmph you will drop the RPM by 500.. and not much noticible power/accelration loss..

i feel that 1st gear is already short.. for a touring bike.. +1 teeth wont affect much.. above that its tried and tested..and also cheaper..
the sprocket would cost you as low as 2k ... hypermile on it when going on trip... if you dont like it.. changing back to stock is 20 minute job..

check out cbr250.net.. people are trying various combo's 14-37 , 15-36(only and only for hypermiling) etc etc..

above that our cbr works on 7-8% of speedo error .. with a 15T in front the speedo and the actual bike speed will we almost same..
----consecutive posts auto-merged-----


you talk of a VFR ?? check out the MT-01 .. it does 200+ at a mere 4000 RPM

----consecutive posts auto-merged-----

bro but the wind shield of the bike looks blackish with reflection.. had it been clear.. it would be transparent...

----consecutive posts auto-merged-----


only place i could figure out a 15T was amazon and few others here n there and tyga in thailand... can you get a 15T for front locally ??

if you can then i am in. infact maybe 10 other folks too...

----consecutive posts auto-merged-----

cbr Speedo already has a 7-8% speedo error.. its over optimistic.. with a 15T in front.. it will become almost 0...

Re: Honda CBR 250R

Sidhu bro, you seem to be good with numbers...But for a backbencher like me, numbers seem to revolve around my head like fireflies...so in simple words, I'd like a more relaxed ride too. How would a 15-37 combo work out? Will that make the ride 90kph@5000rpm? Most importantly, which bike's sprockets would fit the CBR perfectly?

Frankly speaking, 110 @ 4000 rpm does sound too less for a 1200cc hypertourer which costs (almost) twice as a 'busa.