Sprocket

On Feb 22, 3:24�pm, "Blattus Slafaly � � 0/00 "
wrote:

> So if my little sprocket was going 2000rpm's �the back one was going 560
> rpm's and now it's going 623 rpm's.

But the motorcycle is not travelling the same speed. You're looking at
the calculation ass-backwards. You want to calculate the rolling
circumference of the wheel, the number of times it turns when you're
cruising at 100 kph, and look at the effect on *engine* RPM.

>� Should get better fuel mileage now. Not against the law is it?

Depends on what the speed limit is.

This is a speed and RPM calculator. Plug in your primary drive ratio,
gear ratios, final drive ratios, and your rear tire diameter and
decide what RPM you want to look at.

http://www.650ccnd.com/calc.htm
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Ken Abrams wrote:
>
> ""Blattus Slafaly £ ¥ 0/00 "" wrote
>
>> Should get better fuel mileage now.
>
> Maybe, maybe not. More goes into fuel consumption than drive ratio.
>
>> Not against the law is it?
>>
>
> Yes! Bush is sending the FBI to your door as we speak!
>
> It is, however, probably somewhat stupid.
>
> Changing the rear sprocket is more difficult and expensive that doing
> the front.....one tooth.

Depends on the bike. Some require removal of the clutch to replace the
sprocket.

Les
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Ken Abrams wrote:
>
> ""Blattus Slafaly £ ¥ 0/00 "" wrote
>
>> Should get better fuel mileage now.
>
> Maybe, maybe not. More goes into fuel consumption than drive ratio.
>
>> Not against the law is it?
>>
>
> Yes! Bush is sending the FBI to your door as we speak!
>
> It is, however, probably somewhat stupid.
>
> Changing the rear sprocket is more difficult and expensive that doing
> the front.....one tooth.
> You will have less acceleration and might actually find that your
> mileage goes down........depending on what bike you have and how you
> ride it.

I had too much power before this will be better. I had more acceleration
that I needed. I couldn't shift it fast enough And I was always looking
for another gear on the top end and there were no more.
>
> So, if you don't like the result, for whatever reason, now you must
> remove the rear wheel AGAIN to change out the rear sprocket..........and
> a difference of 5 teeth may require a different chain.
>
No, I got a sprocket with the same pitch as the old one to use the same
chain.

> Overall, not a good plan.
>
>
>


--
Blattus Slafaly ? 3 7/8
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Ken Abrams wrote:
>
> ""Blattus Slafaly £ ¥ 0/00 "" wrote
>
>> Should get better fuel mileage now.
>
> Maybe, maybe not. More goes into fuel consumption than drive ratio.
>
>> Not against the law is it?
>>
>
> Yes! Bush is sending the FBI to your door as we speak!
>
> It is, however, probably somewhat stupid.
>
> Changing the rear sprocket is more difficult and expensive that doing
> the front.....one tooth.
> You will have less acceleration and might actually find that your
> mileage goes down........depending on what bike you have and how you
> ride it.
>
> So, if you don't like the result, for whatever reason, now you must
> remove the rear wheel AGAIN to change out the rear sprocket..........and
> a difference of 5 teeth may require a different chain.
>
> Overall, not a good plan.
>
>
>
You can get them here: http://www.sprocketspecialists.com/

--
Blattus Slafaly ? 3 7/8
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""Blattus Slafaly £ ¥ 0/00 "" wrote

> No, I got a sprocket with the same pitch as the old one to use the same
> chain.
>

Ahem. Of course it is the same pitch.....duh.
When the combined TOTAL of sprocket teeth changes by 5 either way, there may
not be enough slack in the adjustment mechanism to allow you to keep the
same LENGTH chain.

I did a similar thing by increasing my front by one tooth. My small
displacement (250) machine is smoother around town but I lost about 5 mph on
the top end. Gas mileage stayed about the same, mostly due, I think, to the
fact that I stay in lower gears longer.
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"Project Magnet #1" wrote

>> Changing the rear sprocket is more difficult and expensive that doing the
>> front.....one tooth.
>
> Depends on the bike. Some require removal of the clutch to replace the
> sprocket.
>

RIGHT ! Thanks for that bit of wisdom.
And for "normal" street bikes, what percentage do you think are built that
way?? 5% ?? Less ??
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Ken Abrams wrote:
>
> "Project Magnet #1" wrote
>
>>> Changing the rear sprocket is more difficult and expensive that doing
>>> the front.....one tooth.
>>
>> Depends on the bike. Some require removal of the clutch to replace the
>> sprocket.
>>
>
> RIGHT ! Thanks for that bit of wisdom.
> And for "normal" street bikes, what percentage do you think are built
> that way?? 5% ?? Less ??

Enough that I own several that require it.
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Ken Abrams wrote:
>
> ""Blattus Slafaly £ ¥ 0/00 "" wrote
>
>> Should get better fuel mileage now.
>
> Maybe, maybe not. More goes into fuel consumption than drive ratio.
>
>> Not against the law is it?
>>
>
> Yes! Bush is sending the FBI to your door as we speak!
>
> It is, however, probably somewhat stupid.
>
> Changing the rear sprocket is more difficult and expensive that doing
> the front.....one tooth.
> You will have less acceleration and might actually find that your
> mileage goes down........depending on what bike you have and how you
> ride it.
>
> So, if you don't like the result, for whatever reason, now you must
> remove the rear wheel AGAIN to change out the rear sprocket..........and
> a difference of 5 teeth may require a different chain.
>
> Overall, not a good plan.
>
>
>
It's harder to get a larger drive sprocket (15 or 16 teeth) without
modifying the chain guard. It's easier to reduce the size of the rear
sprocket to me. Taking off the wheel or shortening the chain is not
rocket science.

--
Blattus Slafaly ? 3 7/8
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"Project Magnet #1" wrote

>>> Depends on the bike. Some require removal of the clutch to replace the
>>> sprocket.
>>>
>>
>> RIGHT ! Thanks for that bit of wisdom.
>> And for "normal" street bikes, what percentage do you think are built
>> that way?? 5% ?? Less ??
>
> Enough that I own several that require it.

OK, you started it, now how about finishing it?
Just exactly what make and model are those "several"?
And why is it that the CLUTCH must be removed to change the front drive
sprocket?
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Ken Abrams wrote:
>
> "Project Magnet #1" wrote
>
>>>> Depends on the bike. Some require removal of the clutch to replace
>>>> the sprocket.
>>>>
>>>
>>> RIGHT ! Thanks for that bit of wisdom.
>>> And for "normal" street bikes, what percentage do you think are built
>>> that way?? 5% ?? Less ??
>>
>> Enough that I own several that require it.
>
> OK, you started it, now how about finishing it?
> Just exactly what make and model are those "several"?
> And why is it that the CLUTCH must be removed to change the front drive
> sprocket?

Older Triumph 650's, the clutch must be removed to get to the tranny
sprocket.
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""Blattus Slafaly £ ¥ 0/00 "" wrote

> It's harder to get a larger drive sprocket (15 or 16 teeth) without
> modifying the chain guard.

Oops! Forgot about that.
At least you won't have to remove the clutch.............like the thousands
of folks who are riding a 30 year old Brit.
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On Feb 23, 8:19�am, "Blattus Slafaly � � 0/00 "
wrote:

> It's harder to get a larger drive sprocket (15 or 16 teeth) without
> modifying the chain guard. It's easier to reduce the size of the rear
> sprocket to me. Taking off the wheel or shortening the chain is not
> rocket science.

Yabbot, figuring out how many less teeth you need on the rear sprocket
might as well be "rocket science", for you at least.

The usual target is one more tooth on the front or three less teeth on
the rear.

This should *optimally* change the cruising RPM in top gear by about
7.5%.

Your selection changes it 11%, and you may find yourself shifting down
from high gear often, unless you have a powerful engine.
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I just read all the replies in this thread, and my head hurts. Why is
that?

One guy somehow switched the topic to removing the clutch assembly and
changing gears in the transmission? How did that happen?

To the original poster....

You went from a 50T rear sprocket to a 45T. Three things will happen
that you will notice right away. Your cruising RPM will be lower. Let's
say that at 60 MPH your bike ran at 6000 RPM, with the first gearing.
After the change, at 60 MPH your engine RPM will be 5500. These numbers
may not even be close, but you get the idea, right?

The second thing you will notice right away is slower acceleration.

The third will be a higher top speed.

I commute 35 miles one way to work on a Suzuki DR200. Not much of a
street bike, not even much of a trail bike, but it's what I've got and
I'm using it. It came with a 14T front and 45T rear. When I cruised down
the road listening to the engine, a comfortable cruising speed was only
50 MPH. At 60 MPH the engine was working way too hard for my taste. So I
installed a 39T rear sprocket. Now it cruises nicely at 60 MPH. And can
even make 70 when needed. Top speed is actually unknown. The speedometer
only goes up to 85, but it would not do that with the original gearing.

So for street use, you did the right thing. For serious dirt and / or
trail riding, you may have made a mistake. I still ride my DR200 on
trails, I just use a lower gear in the transmission then I did before.


"War is an ugly thing, but not the ugliest of things; the decayed and
degraded state of moral and patriotic feeling which thinks nothing is
worth a war, is worse." --- John Stuart Mill: 
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