Question About Gears

[dyehardfan]

Can someone tell me what the difference between the two different gears in the following ebay links would be?

15*81: http://cgi.ebay.com/ebaymotors/honda-sp ... 5636d8cca1

15*82: http://cgi.ebay.com/ebaymotors/Honda-Sp ... dZViewItem

[mousewheels]

15/82 is about a 5.47 reduction ratio
15/81 is a 5.40 reduction ratio

It's just over 1% difference. On an equal engine rpm basis - if at a given rpm 35.0mph was had on 15/82, 35.4 mph would be the result of 15/81.

[dyehardfan]

Thanks. How does this compare with the stock gearing?

I am deciding between the 44mm and 48mm BBKs and figure I might as well upgrade as much as possible while I'm tearing down and cleaning. Either of these two would be an upgrade from the stock gearing I am assuming, no?

[mousewheels]

Thanks. How does this compare with the stock gearing?

Hi - click on the link below, then scroll to the bottom to get to the Spree type single reduction gear set info.
Wiki link for Spree/SB50 transmission ratios

As you can see from the above link - ratio depends upon the year and model of your scooter. Somewhere between 18 to 28% change in reduction ratio with the aftermarket gears. Early Sprees all had a higher reduction. In later Sprees (86/87) Iowa models are the slowest with high reduction gears, restricted exhaust and jetting. A mid slow model with the older high reduction, and those that were out of the box advantaged via gearing.

If you search around, you will find some threads on aftermarket gear experiences.

[Bear45-70]

I thought that Taz was the only one making aftermarket gears for a Spree.

[dyehardfan]

I thought that Taz was the only one making aftermarket gears for a Spree.

Well, there goes the answer to my next question. I was wondering if anyone had shopped with this seller before, or if he/she was a member of the board.

[mousewheels]

Without telling - best I can do is "Search around here and see or ask him"

[dyehardfan]

1986-77 NQ50 A Spree 13 83 6.385 1.8:1 11.49
Aftermarket 15 81 5.40 1.8:1 9.72

So about 15.5% less reduction. This equals a 15.% increase in torque and/or horsepower at the same engine RPM? That seems pretty simplistic. I am assuming you MUST have more power (bigger displacement) to consider moving to one of these gears or I would just end up with a really torquey tortoise?

Thanks. How does this compare with the stock gearing?

Hi - click on the link below, then scroll to the bottom to get to the Spree type single reduction gear set info.
Wiki link for Spree/SB50 transmission ratios

As you can see from the above link - ratio depends upon the year and model of your scooter. Somewhere between 18 to 28% change in reduction ratio with the aftermarket gears. Early Sprees all had a higher reduction. In later Sprees (86/87) Iowa models are the slowest with high reduction gears, restricted exhaust and jetting. A mid slow model with the older high reduction, and those that were out of the box advantaged via gearing.

If you search around, you will find some threads on aftermarket gear experiences.

[odinxxix]

chopchop123 is tazland001 here on the board. pm him

[Bear45-70]

1986-77 NQ50 A Spree 13 83 6.385 1.8:1 11.49
Aftermarket 15 81 5.40 1.8:1 9.72

So about 15.5% less reduction. This equals a 15.% increase in torque and/or horsepower at the same engine RPM? That seems pretty simplistic. I am assuming you MUST have more power (bigger displacement) to consider moving to one of these gears or I would just end up with a really torquey tortoise? .........................................

Not true with both topics. Less gear reduction means LESS torque, not more. Horsepower is not effected by gearing so horsepower does not change from what is available at the crankshaft.

[dyehardfan]

1986-77 NQ50 A Spree 13 83 6.385 1.8:1 11.49
Aftermarket 15 81 5.40 1.8:1 9.72

So about 15.5% less reduction. This equals a 15.% increase in torque and/or horsepower at the same engine RPM? That seems pretty simplistic. I am assuming you MUST have more power (bigger displacement) to consider moving to one of these gears or I would just end up with a really torquey tortoise? .........................................

Not true with both topics. Less gear reduction means LESS torque, not more. Horsepower is not effected by gearing so horsepower does not change from what is available at the crankshaft.

Thank you for the clarification on that. So this means I need the bigger displacement to make up for the lost torque at stock displacement? The gear reduction will only help with top end speed?

[dyehardfan]

chopchop123 is tazland001 here on the board. pm him

Thank you for the clarification. I will do so.

[Bear45-70]

Torque determines acceleration, horsepower determines top speed, if you have enough horsepower to pull the gears to the engines max RPM you will increase your top speed. It has be shown that acceleration suffers badly and top speed does increases with the gear alone, but the loss off the line is way to much to lose. I would not install Taz' gears without a BBK. The Spree is a slug with the stock gearing and you need BBK power to cover the gear change. If you are going to stay with the stock carb and exhaust then go with the 44 mm BBK. If you are willing to go to the trouble of intake, crab and exhaust changes, the go with the 48 mm BBK. Contact Taz via PM and get a better deal than on flea-bay.

http://www.hondaspree.net/phpBB3/member ... ile&u=9513

[dyehardfan]

Again, thanks for the help.

I plan on doing the SB50 intake/reeds/carb, the pulley/belt mod and a 44mm BBK. I would do the 48, but I am more concerned with reliability than I am top end. Might undertake the 48mm one day, but I think I would need to go much further with the intake and exhaust system to truly gain from it form what I see on here.

[zuphilius]

Again, thanks for the help.

I plan on doing the SB50 intake/reeds/carb, the pulley/belt mod and a 44mm BBK. I would do the 48, but I am more concerned with reliability than I am top end. Might undertake the 48mm one day, but I think I would need to go much further with the intake and exhaust system to truly gain from it form what I see on here.

Wow, a new guy actually getting what Bear is laying down, without argument.

My hat's off to you young padawan.