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883, final drive, ratio, sprocket

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  #1  
Old 1 Week Ago
FrankGS FrankGS is offline
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Default 21 vs 22 vs 23 teeth sprocket

Ok I know that this topic has probably been addressed in other threads but, as much as I have searched in the forum, I have not read any posts that also indicate the solution to the question (or simply I'm not able to find them).

My 1986 883 seems to be the model with the highest ratios. Now it is 1200 cc, Edelbrock heads, Andrews V4, Super E: all this, combined with the original ratios, means that I can start from a standstill in second gear without problems.

At 70 mph the engine screams (I don't have the tachometer - soon to be installed - but I suppose it turns between 3500 and 4000 rpm) while in first gear I can tackle a 30% slope uphill with the engine almost idle.

And, of course, the bike does no more than 30 mpg (70% city, 30% freeway).

Obviously, the final ratio must be changed: the minimum is to change the final drive sprocket with the one with 22 teeth, however, may it be worth going directly to 23?

Have any of you tried and verified the differences in terms of revs in fourth gear with a 22 or a 23 teeth sprocket?

Thank you.
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  #2  
Old 1 Week Ago
kitabel kitabel is offline
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tried and verified the differences in terms of revs in fourth gear

The difference in RPM, in any & all gears, is the ratio of old teeth ÷ new teeth.
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  #3  
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FrankGS FrankGS is offline
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Default

Quote:
Originally Posted by kitabel View Post
tried and verified the differences in terms of revs in fourth gear

The difference in RPM, in any & all gears, is the ratio of old teeth ÷ new teeth.
So, basically, 21/23=0.91, that means that given the same speed, with a 23 teeth sprocket the rpm are 9% less than with a 21 teeth?

Cool, I wonder what kind of impact could this have on the acceleration.
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XL1275 XL1275 is online now
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Quote:
Originally Posted by FrankGS View Post
So, basically, 21/23=0.91, that means that given the same speed, with a 23 teeth sprocket the rpm are 9% less than with a 21 teeth?

Cool, I wonder what kind of impact could this have on the acceleration.
Yes, and 1200s have different primary ratios too. Not sure about your year though.
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  #5  
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Default

Quote:
Originally Posted by XL1275 View Post
Yes, and 1200s have different primary ratios too. Not sure about your year though.
It seems they are the same: http://sportsterpedia.com/doku.php/t...o:transfinal01
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Quote:
Originally Posted by FrankGS View Post
Yep, I have an 07 so that was what was on my mind. Sorry.
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Torque in all gears is reduced by the same amount, the engine "feels" smaller. It only really matters in 1st, since in the upper gears you can downshift as needed. Theoretical top speed is increased by new ÷ old.
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On Ironheads, 1 extra tooth on the drive sprocket will lower RPMs at any given speed by about 150-200 in fourth gear. I don't have a chart for any other models unfortunately.

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lower RPMs at any given speed by about 150-200 in fourth gear

This is not possible,.
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I made some calculations, I just have to find that sheet of paper. I'll post when I find it!
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