Unicorn

Since my experience with 14T/42T was horrible I changed from 42T to my ambitions 14T/38T and this time the result is absolutely AMAZING, the acceleration is wonderful. Also the handling, response has got better; may be the handling thing is psychological but I am very happy with the current setup. One and half hours of hardwork removing tyres and sprocket drives of both the vehicles and greasy hands has paid.
Didn't test for topend loss if there is any but I am getting nearly 50~55kmph@4000RPM

^Interesting. Let me know when you get to test top end speed.

First of all Unicorn comes with 15/42t for old gen's where the gear ratio is 2.8... When you change it to 14/38t the ratio will be 2.7 which is something close to 15/41t... Here you will be gaining top end with negligible drop in acceleration .

There is no way you can gain acceleration. Try for yourself, put 42T at back and 14t at front and then tell the acceleration difference. If you really want some super acceleration on Unicorn, then plonk in classic CBZ's sprocket which has 14/46t.

On my Uni I have used some of the combinations and I can vouch for the statement I have given.
15/42t - stock.
14/42t - Better acceleration.
15/38t - better top end but worst acceleration.
14/38t - slight drop in acceleration with very little increase in top end.

Have tried a friend's Uni with 14/46t of cbz classic where his top end was limited to 90's but acceleration was outstanding.

I know the math contradicts here, but I was running on 15/42T and had complained about the acceleration and response of the UNI with respect to Ambition in the forum somewhere. so after going through some threads regarding sprockets I changed to 14/42T and as mentioned in the previous post the engine RPM is always higher and I didn't enjoy the acceleration. I was so irritated by 14/42T that I changed to my ambitions 14/38T and now things are great. I also couldn't understand why it happened after calculating the gearing ratios..... hey the ambitions rear sprocket drive's diameter is smaller than Uni's I think; will confirm later. May be this also has something to do with the acceleration, doesn't it? For one turn the 1st wheel in the picture turns .75x say, but for the same one turn the 2nd wheel turns only .60x....sheer assumption..

Yes, Ambition's rear is smaller than Uni's. Infact it depends on number of teeth. 46T is bigger than Uni's.

Smaller the rear lower the acceleration, bigger the rear higher the acceleration. When your acceleration is improved your rpm will be more than what you attain in stock.

How come? I am not going here by the rules of sprocket teeth, ratios etc at this moment. From my picture

case 1 - Both wheels are of the same size. sizeof(a1) = sizeof(b1)
so if a1 rotates one cycle - b1 also rotates one cycle

case 2 - sizeof(b2) > sizeof(a1)
so if a1 rotates one cycle - b2 rotates only 3/4th of a cycle

since the tyre size is the same: in Case 1 the tyre covers more distance than in Case 2 for the same rotation of the front wheel/sprocket.

I still don't know if this can be attributed to speed or acceleration. very confused ... will have to take some readings of the speed, RPM then I can come to some conclusion. but at present I am feeling good with my bikes condition.

You have the answer in your statement. When the rear is small the wheel covers more distance but the time taken to attain it is more but better top speed. I don't know to explain with maths funda yar. Sorry

In Case 1 for 1 rotation of a1 - b1 completes 1 rotation - cycle ended in timeperiod T.
In Case 2 for 1 rotation of a1 - b2 cannot complete 1 whole rotation but only a part of it-implies cycle is not completed which in turn implies for b2 takes more time to complete the whole rotation so here the timeperiod is > T

so Case 1 takes less time to cover the distance...so more acceleration.

Let me put this in another way.

Since the front sprocket will be the same for both the cases, all the components Linear velocity, angular velocity, radius will be the same.
This Linear velocity will be converted to angular velocity at the rear sprocket.
And angular velocity and Linear velocity are related by V linear = r(radius) * w(angular velocity)
hence angular velocity w= V linear/radius since V linear is constant; angular velocity is inversely proportional to the radius of the rear sprocket. so bigger sprocket means less angular velocity.

Can this be translated to acceleration???????????????
Any physics gurus????????

14/38T
I gave my bike to my friend for his opinion. He has rode my Uni earlier and used to say It is difficult to dodge the traffic and overtake someone easily - waste bike, today he said it is much better than earlier but not as good as his extreme.

This is the first thing Ive done - change to 14/42T. As I already mentioned - the acceleration improved but the feel is irritating, I mean engine running at higher RPM and the smoothness of Uni was gone.

I tried these so far.
15/42T - yeah stock/waste
14/42T - yes better acceleration but bike felt noisy/feel of ride is annoying.
14/38T - 0-20kmph same as stock, 20-70kmph - very very comfortable; very good combination of acceleration and speed. please don't say there will be no acceleration gain. Tested by me and cross checked with my friend. Math failed here.
14/43T - super acceleration/felt like competing with other bikers on the road. I lured my friend who is riding CBZ Xtrem with a slight gain in mileage and exchanged my 15/42T with his 14/43T.
15/38T - Cannot try this - Fitted back 14/38T to my ambition and cannot go through the labor again.
14/46T - I don't want a dirt bike.
15/43T - will try this tomorrow.

And yes you are correct. Bigger rear - more acceleration. when I fitted Uni's 42T to my ambition and released the clutch as I used to do when using 14/38T, the tyre leaped 2 inches into air.

Bottom Line : for my Old Unicorn 14/38T worked good so far minus testing with 15/43T.

15/43T is the stock setup of Unicorn (3rd and 4th Generation).
Results in slightly better acceleration than 15/42t !

The same will / should have happened when you tried 14/43t as well !! Here the rpm will shoot up more than 14/42t.

I just want a simple thing from you to do. If you are still experimenting. Please note down the engine rpm with all different combination of sprockets at any particular speed say 80.

Mathematics can't be wrong but the calculation you did might be wrong. As I said not much into maths so won't discuss on mathematics !!

I have a 2010 Honda unicorn with stock gearing...i wanna upgrade to a bigger rear sprocket and a shorter one on front to increase acceleration...so plz suggest me a appropriate sprockets size...Plz give your suggestions regarding cbz classic rear sprocket(46T).Are they direct fit or i have to change the chain also...??

Thanks in advance....plz help.

Not much into sprockets, but AFAIK we should change the chain and sprocket together. You may keep the old chain for future.
In case, you're buying the OE sprocket (stock), you may keep the old chain with maybe a couple of links removed. But you'll end up buying the chain eventually.

Also, go through this page - http://www.xbhp.com/talkies/motorcyc...er-cbf-44.html

Re: Unicorn sprocket change

Hi guys...
I have changed chain sprockets of my uni 2009 model with CBZ 14T-45T I feel gain in acceleration but there is a major drop in top speed and mileage. I used to get 56kmpl but now I am getting less than 40kmpl. Its so horrible. Please suggest me a good solution I need more mileage than acceleration as I travel 150kms daily.

Thanks in advance...

Re: Unicorn sprocket change

^Old or spokes model Unicorn came with 42T at the rear and alloy model released after that was with 43T. Go for 42T sprocket kit(you'll need to hunt), won't regret. It would offer good mileage per litre of petrol and on highways 42T will improve your top end. Initial pickup will be slightly sluggish from present sprocket output.