Gear ratio question - Steve Saunders Goldwing Forums

 
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post #1 of 7 (permalink) Old 10-24-2006, 11:07 PM Thread Starter
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I swapped the 83 engine with a 81 engine.

The rpm's are much higher at highway speed now. I have the final drive from the 81 (whether it will fit the 83 I dont know yet) and trying to figure out if swapping it will lower rpm's.

Clymer manual says 81 final drive ratio is 3.091, 83 final drive ratio is 3.100
Could these numbers also be expressed as "309" and "310" gears like it is on cars?
If this is right, is 309 going to make the tire turn faster or slower at a given rpm?

1983 GL1100 Interstate with 1200 engine, single carb, and C5 ignition.



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post #2 of 7 (permalink) Old 10-24-2006, 11:50 PM
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The difference in gearing is in the gearbox, the difference in the final drive is pretty negligible. You can call them 309 and 310, means the same thing. As you can see by the numbers there's less than 1/3 of 1% difference in gearing in the finals, that's going to make hardly any difference. I don't have my reference handy so I don't know if there's any difference in wheel size.

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post #3 of 7 (permalink) Old 10-25-2006, 09:29 AM Thread Starter
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exavid wrote:
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The difference in gearing is in the gearbox, the difference in the final drive is pretty negligible. You can call them 309 and 310, means the same thing. As you can see by the numbers there's less than 1/3 of 1% difference in gearing in the finals, that's going to make hardly any difference. I don't have my reference handy so I don't know if there's any difference in wheel size.
Still, any little bit will help. The slower rpms and the subtle hum it had before is what I liked so much about this bike. At the higher rpm on the highway it's more like a crotch rocket than a Goldwing.
The rear tire is 1" larger on the 81.
I hope together with that and the small gear difference it'll be near what it was.

1983 GL1100 Interstate with 1200 engine, single carb, and C5 ignition.



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post #4 of 7 (permalink) Old 10-25-2006, 10:00 AM
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dan filipi wrote:
Quote:
I swapped the 83 engine with a 81 engine.

The rpm's are much higher at highway speed now. I have the final drive from the 81 (whether it will fit the 83 I dont know yet) and trying to figure out if swapping it will lower rpm's.

Clymer manual says 81 final drive ratio is 3.091, 83 final drive ratio is 3.100
Could these numbers also be expressed as "309" and "310" gears like it is on cars?
If this is right, is 309 going to make the tire turn faster or slower at a given rpm?
Dan you can't JUST figure the final drive gear ratio like you do in a 1 to 1 high gear automobile rear gear set.. Your trans output shaft isn’t 1 to 1 like a lot of older cars so doesn’t spin at engine RPM’s in high gear.. There is a basic primary chain ratio between the engine & trans, the trans gearing itself is different, & an output gearing reduction it must ALL go through before it even gets to the final drive.. To get usable numbers you must figure the entire gear reduction between the engine crankshaft & final drive then factor in the rear tire size for ground speed per engine rev..



I don’t have the gearing differences handy here but if you need them I can probably find them in my archives at home for you..



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post #5 of 7 (permalink) Old 10-25-2006, 01:11 PM Thread Starter
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Twisty,
I think I understand what your saying.
It would be interesting to know those numbers.
It all works together as a final factory design gear ratio to tire speed/engine rpm, torque etc. but doesnt it make sense (just like a larger pully will turn a device slower like on a belt driven motor) that a larger tire will turn slower without changing anything else?
One member says roughly 500 rpm slower with a 1" increase in tire size.
That together with a slightly lower ring and pinion ratio I dont see any need to concider the internal gear ratios.

I'm sure there are torque/horse power factors that come into play also.There is a very noticable increase in torque now with these gears, so much so I can upshift 2 gears at a time then into 5th at 40mph, the engine never lugs and I find myself having to shift up and down so often I get a cramp in my hand.
The ratio is so low now I got the front tire to leave the ground into second fully dressed.

With all of these factors to concider I need to go thru the final drive, rear bearings and brakes anyway for service so I have nothing to loose by doing a swap, can always swap it back.

1983 GL1100 Interstate with 1200 engine, single carb, and C5 ignition.



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post #6 of 7 (permalink) Old 10-25-2006, 02:26 PM
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dan filipi wrote:
Quote:
Twisty,
I think I understand what your saying.
It would be interesting to know those numbers.
It all works together as a final factory design gear ratio to tire speed/engine rpm, torque etc. but doesnt it make sense (just like a larger pully will turn a device slower like on a belt driven motor) that a larger tire will turn slower without changing anything else?
One member says roughly 500 rpm slower with a 1" increase in tire size.
That together with a slightly lower ring and pinion ratio I dont see any need to concider the internal gear ratios.

I'm sure there are torque/horse power factors that come into play also.There is a very noticable increase in torque now with these gears, so much so I can upshift 2 gears at a time then into 5th at 40mph, the engine never lugs and I find myself having to shift up and down so often I get a cramp in my hand.
The ratio is so low now I got the front tire to leave the ground into second fully dressed.

With all of these factors to concider I need to go thru the final drive, rear bearings and brakes anyway for service so I have nothing to loose by doing a swap, can always swap it back.
Dan, I found the data sheet but it is in Excel format.. I tried plotting it out here in a reply post but the data is all skewed & not in the correct order.. If you can open an Excel spread sheet give me a PM here or E-Mail with your home E-Mail address & I will gladly send it your way.. If you can't use the Excel format then let me know what format you need it in & I will try to plot it out in that format & send it your way..



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post #7 of 7 (permalink) Old 10-26-2006, 12:00 PM Thread Starter
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I made the switch of the final drive and rear wheel and now at 60 mph it's right around 3500 rpm.
I can live with this.
From what I can remember the all 83 gears set up was closer to 3000 rpm but this gearing now is actually a better match up than 83 stock for the way I drive.
Originally I had to slip the clutch quite alot on launch with alot of gear clatter if the revs were below 3000.

What is a good site to look at tire options, the 83 tire was fatter, I like that look.

Thanks for the help guys.
twisty, that spred sheet is great. It's interesting to see the different years specs.
What surprised me is the 1000's are rated 3 HP higher than the 1100's and Honda finally decided on a 2.833 final drive in '84 after playing around with it in prior years.

1983 GL1100 Interstate with 1200 engine, single carb, and C5 ignition.



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