matching rear sprockets

[Scorpio1963]

Hey guys Im wanting tp upgrade my rear sprocket from a 37t to a 39t.What years will interchange for an 81?Is there any differeces between 77-78 that would be compatible for the 81 year special.I found 1 on Mikexs that has the right teeth count but says it fits earlier models.
Also I have no idea on whats a good brand and is there any other online stores that I can use for shopping to find what Im looking for?Thanks.

 

[xschris]

If you are looking to drop rpms then a 37 tooth is what you want. The 80-82 bikes use a dished sprocket to off set the wider 16" wheel. The 77-79 will work but will be close to the tire.

 

[xschris]

http://www.xs400.com/forum/showthread.php?t=10353&highlight=sprockets The thread where I talked about this already

 

[Scorpio1963]

The 37 tooth sprocket is stock gear from the factory is it or not?I ask this because this is already what I have its just completely worn out.

stock teeth are 16t front and 37t rear

http://www.motorcycleforums.net/forum/paddock/48391-sprocket-question.html

Heres part of an old thread that I had found earlier

For more top speed you would want to decrease the number of teeth on the rear, or replace the rear with the same and put one with a tooth or 2 more on the front.. vice versa for more torque/acceleration witjh a little less top speed. Its all preference which to do but ive read on this forum that the front is easier to change and swap out if you dont like the result

So I have been looking for a rear sprocket with more teeth but they are either difficult to find or much more than Im willing to spend.
So plan B is to go with a 37teeth rear again and go with a front that has more since its much easier to find and like as mentioned easier to change.
Also I have a question about aluminum sprockets,my concern about them since aluminum is much softer than steel wouldnt they wear out faster or not?
Then theres another question about chain length would the stock size fit with these sprockets or am I going to need a longer one?
Also my gear is not offset as shown in the picture.

 

[Scorpio1963]

Heres a pic of my rear sprocket

 

[Lou Ranger]

So I have been looking for a rear sprocket with more teeth ...
So plan B is to go with a 37teeth rear again and go with a front that has more ...

Then theres another question about chain length would the stock size fit with these sprockets or am I going to need a longer one?...

This could be a misprint, but just in case it is not, I wanted to point out that your plan "B" will have the exact opposite result to that of your first plan.

Increasing the number of teeth on the rear sprocket will increase your rpms at a given cruising speed.
Increasing the number of teeth on the front will decrease the number of rpms at any given speed.
If reducing the revving is what you are looking for (as was the case with me), then you can achieve this by lowering the teeth count on the rear sprocket - a 35 or even a 34 if available.
If reducing the revving is what you want, then a 17T front is the easiest and needs only a slight increase in chain length - basically one extra link. But since that means only half a link on top and half on the bottom, I was able to use the same chain by simply moving the rear wheel forward about 1/4".
If you reduce the revving by lowering the rear tooth count by 2 or 3, you would have to move the rear wheel back by maybe 1/2" or more - or grind off one or two links.

But, if you want more revving = all of the above, except the opposite.

 

[Scorpio1963]

This could be a misprint, but just in case it is not, I wanted to point out that your plan "B" will have the exact opposite result to that of your first plan.

Increasing the number of teeth on the rear sprocket will increase your rpms at a given cruising speed.
Increasing the number of teeth on the front will decrease the number of rpms at any given speed.
If reducing the revving is what you are looking for (as was the case with me), then you can achieve this by lowering the teeth count on the rear sprocket - a 35 or even a 34 if available.
If reducing the revving is what you want, then a 17T front is the easiest and needs only a slight increase in chain length - basically one extra link. But since that means only half a link on top and half on the bottom, I was able to use the same chain by simply moving the rear wheel forward about 1/4".
If you reduce the revving by lowering the rear tooth count by 2 or 3, you would have to move the rear wheel back by maybe 1/2" or more - or grind off one or two links.

But, if you want more revving = all of the above, except the opposite.

Si If I lower the teeth count on the rear from a 37 to 36t and leave the front alone does this acheieve lower high rpms at faster speeds?
Im stil confused on xschris pics,I know hes right about the sprocket being countersunk for year my bike is but I can figure out why mine is not?Im thinking maybe the PO has changed it.

 

[Maxim-umm]

Lowering the tooth count on the rear INCREASES rpm's. Increasing tooth count on the front DECREASES rpm's.

 

[Scorpio1963]

Yeppers Im just shopping around trying to find the best deal.

 

[willem]

Lowering the tooth count on the rear INCREASES rpm's. Increasing tooth count on the front DECREASES rpm's.

half true, half false. Lowering tooth count on the rear DECREASES rpm's.

increasing tooth count on the front does the same.

Or the other way:

increasing tooth count on the rear INCREASES rpm's

lowering tooth count on the front increases rmp's also.


It's usually better to change the tooth count on the rear sprocket first. If you're still not happy with your rpm's you could also change the front sprocket size.

 

[willem]

Si If I lower the teeth count on the rear from a 37 to 36t and leave the front alone does this acheieve lower high rpms at faster speeds?
Im stil confused on xschris pics,I know hes right about the sprocket being countersunk for year my bike is but I can figure out why mine is not?Im thinking maybe the PO has changed it.

lower rpms at high speeds, yes

 

[Lou Ranger]

Lowering the tooth count on the rear INCREASES rpm's. Increasing tooth count on the front DECREASES rpm's.

I don't believe this is right.
Since rpms are partly a function of the ratio between the front and rear sprockets, then you have to do the opposite to the other sprocket to get the same effect, not the opposite effect.

Closing the ratio from standard 16/37 makes the bike accelerate a touch slower, but then it runs at a lower rpm at any given speed (2 examples: 17/37, 16/34). Closing the ratio means the rear tire goes farther for a given rpm, therefore, at a given speed, less engine rpms.
When the front sprocket gets an extra tooth, the rear wheel will go about 2.5 links farther for the same amount of turning by the front sprocket. If you leave the front alone and reduce the rear by 3 teeth, it means that the front has to rotate about 1.4 chain links less to make the rear wheel cover the same distance.

@Scorpio - as to your question regarding dished or not dished sprocket, does your bike have the 16" wheel xsChris also spoke about?
Not sure if there were 2 versions ever in one year but, if so, then it would be both the year and the 16"wheel which would dictate an offset. If you have 16", then likely a PO made an error. I'm sure it works okay, however, after my chain break this spring, I did a lot of reading and found a lot of folks warning about proper chain alignment. If it is the least bit crooked, it would be straining one side more than the other - not much, but it would. Not sure if you could feel it as a vibration, since the amount of offset is small relative to the distance between the sprockets, but straight is always better than crooked when mechanical force is involved.

 

[Scorpio1963]

Now can somebody tell me the best online store for ordering these parts.
Old bike barn sucks,Mikes has parts but fail to give a good description on what parts match
Also are our bikes 530 pitch or 520?Trying to find what I want vs what the stores carry is frazzling my mind.
Would hopefully like to have my sparts shipped next week so I can get my bike going again soon.

 

[Lou Ranger]

I believe all our bikes are 530 which is thicker and requires the wider chain. The dohcs are 530 at least.
Is there not a bike shop near you? Even if you don't buy, you could simply go to the parts counter and at least compare one with the other. Use your offset dilemma as your excuse for not buying if their price is too high. Maybe it won't be. I found the local shops are competitive if you count shipping small orders into the price and if you place even a small value on getting it now instead of next week. Winter, after all is coming!

 

[Scorpio1963]

Mostly all the bike parts shops are Harley Davidson stuff

 

[Maxim-umm]

Thanks lou! That's what I get for not double checking

 

[Scorpio1963]

Lou Ranger @Scorpio - as to your question regarding dished or not dished sprocket, does your bike have the 16" wheel xsChris also spoke about?

Yes the bike has the 16 inch rear tire.

 

[Lou Ranger]

Thanks lou! That's what I get for not double checking

Seems we both deserve and live up to our signature lines . .

 

[XSLeo]

I don't know if this will help, reducing the rear sprocket one tooth drops rpms at 55-60 mph about 100 rpms. One tooth change on the front is equal to about 200 rpms.
So if you want to drop 400 rpms drop four teeth off the rear or add two teeth on the front.
On the chains the 5 in the 520 or 530 is the length of the link in 1/8's of an inch, so the 5 is 5/8 inch length. This is the pitch of the chain.
The 2 or 3 in the chain size is the width of the chain in 1/8's of an inch. As in 2/8 or 3/8 wide. The 520 chains and sprockets weigh less than 530 chains and sprockets.
Most alloy sprockets are hardened so the last about the same as steel but cost more. They are also much lighter than steel.
The 0 is just there to make it three digits. Some chains are like a 525 or 425 size. These are pretty much specialized chains for racing applications.
Leo

 

[MrStubb]

As for sprocket sizes and rpms. If you look at a 5 10 or 12 speed bike the smaller the rear sprocket the higher the gear. And the smaller the front sprocket the lower the gear. Take a ride on a bike and pay attention where the chain is when you start off then change gears to the top gear and check the chain track again. You are working harder to make more speed but you are pedaling slower (lower rpm) with the smaller rear sprocket.