Downsizing sporkets ratio..Needs help..

[All Blacks]

Hi Guys,I am planning to downsize my sporkets from a 14-45 to a 15-42.
Reason being is that currently i'm running @ 100km/hr @6800rmp and i find it kinda high and  really stressing while cruising in between 100km/h and 130km/hr.I used to be cruising  at 100km/h at 6200rmp till the day  i did a modification on my dogbone to raise my tail board.This is where i experience  the drastis increase in the Rpm.I'm looking foward  to achive   lower rpm while cruising and is more particular on the top end rather then torque.Is it a wise idea?

[PitterB4]

Huh?  Changing dog bones isn't going to impact your gearing one bit.  You must have changed something else.

That aside - your proposed change seems dramatic.  I'm not smart enough to tell you how many RPMs you'll drop at a given speed but that just seems like a lot.

[All Blacks]

It does not affect the gearing but it somehow or rather streached the chain tention..When parked on mainstand,the rear tyre will touch the ground and the chain looked very slack,but during riding,the chain seem to be have right tension..Been experiencing this for quite some time..Any ideas to overcome tis ?

[Thief400]

It does not affect the gearing but it somehow or rather streached the chain tention..When parked on mainstand,the rear tyre will touch the ground and the chain looked very slack,but during riding,the chain seem to be have right tension..Been experiencing this for quite some time..Any ideas to overcome tis ?

Ya put the old dog bones back in !!!!!!!!

[bonobandit4]

Am I understanding this right?  Don't lots of European modders change their frame geometry this way when going for that hard core street fighter look.  Or does it just appear that way when you see a short tail?  I wouldn't think it would have much effect either, but if you changed the angle from a fulcrum that isn't inline with the sprocket center, you could change the chain tension...  my guess added slack.

[Racerruss-ducati]

This change in gearing will put you at 5924 (~13% change to final ratio) rpm at the same speed at 100 km/hr (if you indeed started at 6800 rpm)  

I still don't understand the dogbone comment either, did you put a new tire on as well?  I went to a 150/60 17 on my bike and it did increase the rpm enough to be noticed, the new tire was 4" smaller in circumference which is only a 5.6% change.  That would seem to be in line with the 6400 to 6800 rpm change you noted.

[Herr Tod]

14-45 with a 150/60 rear tire makes 100 km/h at 6500 RPM

15-42 with a 150/60 rear tire makes 100 km/h at 5650 RPM

[Krautwagen]

Changing chain length or swingarm geometry has nothing to do with changing revs.  Yes, as stated above, it can change the chain tension, but that's why you re-adjust it.  

The only way it can vary is by changing sprocket or tire sizes.  Keep in mind if you change the front tire, your speedo can be off.

[Red01]

The B4 can run 6800 rpm all day long . . . you're only a little more than halfway to redline there.
Not at all high or stressful for this motor! It's built to rev.

I have a feeling you would not be happy with the performance of the bike with such tall gearing. Starting off will involve more clutch slipping, especially on uphill grades and you accelleration will suffer.

[All Blacks]

I  actually used the same dogbone as i drilled another hold below the original one.I did not change anything else..I've tried putting the bone to its original hole and the bike was extremely low and i will tend to hit my header when passing through high humps..I tink its just my feeling tat i find the engine sounding stress while cruising @ 100km/h..I tink i will try to adapt to that..

[All Blacks]

Btw...Tis is my bike pictures...from the day i got it till the present..along with the changes..Notice the rear tyre not touching the ground  and am not touching the after the dogbone mod.

[gsxr400 racer]

Hi Guys,I am planning to downsize my sporkets

Those are my favorite tool to eat with , If you find a bigger one let me know. I always felt if i could find a bigger spork i could get more in my mouth!

Sorry , had to do it i get it all the time!lmao

[PitterB4]

Hi Guys,I am planning to downsize my sporkets

Those are my favorite tool to eat with , If you find a bigger one let me know. I always felt if i could find a bigger spork i could get more in my mouth!

Sorry , had to do it i get it all the time!lmao

LMFAO!

Great fairing!