some help on sprockets please

[CyberTron]

Hi!

I have driven my new TMS (QingQI) 200cc for around 1000km now and i am thinking of regearing it a little.

but how?

I have 15/48 on now.

15/48 = 3,2 STOCK
15/45 = 3,0
15/42 = 2,8

16/48 = 3,0
16/45 = 2,8
16/42 = 2,6

a little question, does it matter if i go two tooths down back or 1 up front?

Now since it is hard to get a rearsprocket for my bike (dr200's are not common in sweden and my bike is a copy of that)
i am thinking of buying a 16tooth front.

I have these speeds today with 15/48 (the rpm's are not exact but somewhere around that), what will my new rpm be if go for gearratio 3.0 instead of 3.2? anyone care to take a guess? or must I have a gear ratio of 2.8 for it to go smooth in 90/kmh my goal is to get 90km/h around 4000-5000 rpms.

100km/h = 7000rpm
90km/h = 6500rpm
70km/h = 5500rpm
50km/h = 4500rpm

sorry for the long post and for spelling/grammar.

[czowner]

I believe that most people with 200cc go for a 17:44 combination, my 223cc which has more torque at lower rpm runs 17:42 and it is very happy at 100kph.
Here's a list of alternative sprockets:

All information courtesy of JT Sprockets, (so if it's wrong don't blame me).

Front
Reference no. 264-**.

17 Yam DT 125 Tenere '89, Honda CD 175 A/A4/K5 '71-'78, Derbi Senda 125 SM/R '04-'05

16 Gilera Cougar 125 '01, Honda CB 175 K3/4/5/7, Yam DT 125 LC/Z '88-'93

15 Honda EZ90 Cub '93-'96, Kymco 125 Pulsar

Rear
Reference no. 269-**

40 Honda CB 100 K1/2

41 Kymco Zing '97-'98, Honda CG 125 (Brazil)

42 Honda CB 125 Superdream '82-'88, Honda CB 125 Benly '82-'85

43 Honda XL 125 K2/3 '78-'79

44 Honda XL 100 SA/SZ '78-'80

45 Honda XL 100 S '79-'80

46 Kymco Stryker '99-'03

(** no. of teeth)

[CyberTron]

hi

thanks, but isn't those for honda clones? mine is a Suzuki DR200 clone (but might have the same sprockets anyway ) although that JTsprocket page is great!

[fatboy250]

This would be how I would go about choosing new sprockets

Originally Posted by fatboy250

The only problem is that to truly evaluate the final gear ratios (sprockets) you need to know the final ratios of the output shaft coming from the transmission of each bike...just as Red mentioned. Remember, most of us are without a tachometer. So we can't give a you a standard "6500 rpm/mph" reading.

I think the easiest thing to do is find out what you have when you ride yours and decide if you want to change your ratio once you've ridden it. The math isn't that difficult if you know your stock gear ratio and what speed feels comfortable on the engine [desired rpm]. You can simply create [with a sprocket change] the gear ratio needed to then go the speed that you want to go at that [desired rpm]. Remember this is probably going to be different for a guy that is 160lbs compared to someone who is 265lbs. So you have to figure it out for you and yours.

For instance, if all I wanted to do was change my rear sprocket which is 46. And I know that 55 is the comfortable cruising speed [desired rpm] And I would like to go 65 at the same comfortable cruising [desired rpm]
Then it would be simple algebra 55(46)=65x => (55/65)(46)= x => 38 or 39 tooth sprocket.

Luckily my stock sprockets 14/46 are perfect for the type of riding I do. Like Red said the 55mph cruising speed feels comfortable on the Roketas.

Jason

[CyberTron]

that is great fatboy

i will calculate and try