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Tweaking sprocket gear ratio question(s)

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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Trying to calculate the sprocket tooth ratio needed to get a 70 mph speed at 4000 rpm on my 1100.
I am pretty sure it currently turns 5000 rpm at 70 mph with the stock 15/42 ratio or 2.8.
So I figure if I want to achieve 4000 rpm I need a 20% reduction or .56. So my target ratio is 2.24?
According to the chart I have this can be done with a 17/38 setup.
Is my math correct? It feels just a little too simple (linear) to me for something involving ratios.
Does anyone know if there will be a problem with using a front sprocket two teeth over stock?
In thoery I think a standard 96 link chain should still work. I assume I would just need to set a new mark on the swingarm for the starting point when first installed as opposed to using the scale on the decal that indicates chain wear/life.
Thanks.
 
As I bought my GS1150 1984, the front sprocket was one toth over stock, I didn't like that ratio, because it fealt that I had to slip to much on the clutch every start and replaced it back to stock, got the old stock sprocket then I bought the bike.

It was no problem at all using the same chain, and there was still space left, but I havn't tried with two teeth over stock.

BTW:

Are you sure you want as much as two teeth over stock?

BTW2:

Could you please look what your country code is of your GS1150 ES 1984?
 
kz said:
BTW:

Are you sure you want as much as two teeth over stock?
Click to expand...

I really don't know. I guess going with less teeth on the rear would get the same thing. Maybe a 16/36. And maybe getting to 4000 rpm at 70 mph will be too "tall" of gearing for lower speeds and take off. I don't really care about hole shots or 1/4 mile speeds. But like you mentioned, I don't want to have to slip the clutch a lot to get rolling.


kz said:
BTW2:

Could you please look what your country code is of your GS1150 ES 1984?
Click to expand...

The VIN is JS1GV71A4E210XXXX. This is what is stamped on the steering head. No plate or decal like my 1100 has. Just the stamped number.
Is there someplace else to look for a coutry code?
It also has the air forks. But I don't see anything on them about being "Canadian Only". Don't now if that matters or not.
Carbs are stamped with 00A10 421.
Hope this helps.
 
What are you aiming for by changing the ratio?

Less vibrations, fuel consumption, top speed?

Do you drive mostely in town or on highways?

In my opinion the bike was OK to drive with one more toth on the front sprocket, but for my taste, and a lot of driving in the town, traffic lights etc. it was to much clutch slipping.

All this goes for my GS 1150 1984


BTW2:

Thanks for the codeinfo, I'm unsuccsefully trying to figure out my own country code, now I'm trying a new method; excluding all non-Sweden codes.

Don't know where the code should be written....
 
kz said:
What are you aiming for by changing the ratio?

Less vibrations, fuel consumption, top speed?
Click to expand...

Mostly wear and tear on the engine and fuel consumption.
 
I would try one tooth over stock first, easy to install and then you can experience if you like the new ratio.

If you feel confident with the ratio, is individual, as driving behaivor, passenger or not and so on all influates if you like the new ratio or not.

1000 rpm is more than the difference between the 4th and 5th gear....
 
PJ,

Your math is correct. If that's the gear you want then go for it. I went to a 16 tooth counter sproket and didn't like it. I like hole-shots and wheelies.
Don't worry about the marks on the swingarm. Use them as a reference only or not at all. Mark the center of your axle and swingarm bolts and measure to set you chain tension to 5/8". This is much more acurate.

Steve
 
Sorry I didn't mentioned it before, but I also think your math is correct.
 
will a 16 or 17 tooth front sprocket fit on a gs-1150?

will a 16 or 17 tooth front sprocket fit on a gs-1150?

I have ordered a 16 tooth for my 1986 gs1150ef but some of the parts books say it wont fit. The stock 15 tooth is on there and has a very tight clearance to a case bolt at the back of the cover. There is only about 3/16 inch there now. The 16 tooth gear must be bigger?? Do you cut the bolt out or will it fit? Also what is with all the foam inside the cover that sits over the front sprocket? Is this for noise? :?:
 
My '79 GS1000 had this foam inside the front sprocket cover when I bought it. It's supposed to deaden noise from this area. Mine was half dried-out and dripping wth old chain lube, so I just removed the whole lot- takes a while.
No increase in chain noise!
 
You might have to go to a 530 chain to run that many teeth on the front sprocket.
 
I know a 530 fits...You can grind quite a bit of material off the inside of those sprocket covers..A Dremmel or die grinder works just fine.
 
running a 17 tooth on the front of my 750 I had to carefully grind away some of the housing around the bolt on my cover. I only took enough for clearence.
 
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