[VTX BILL]

Switched final drives on my 1800 N. Installed a 1300 final
Previous forums stated that the switch would give better fuel economy.
Right out of the gate I noticed that shift distances were much shorter, which is a concern
Is there something I am missing in the swap? Was there another step to the process?
It's going to be in the 60's in Northern Illinois today, so I am going to head out and run through a couple of tanks to see what happens.

I will also be taking a GPS to check speedo differences. I will report back.

 

[PaXman11]

There is a couple hundred rpm difference in the 2 rears. But it seems if you wanted better mileage, you were mistaken. The 1300 rear on the 1800 shortens the operating range in all gears. In other words, you get better take-offs, better accelleration, but slightly worse mileage. Using a muscle car as an example, it would be like swapping a 3.55 or 3.73 rear gear for a 4.10 or 4.11. Now, for a 1300 owner to swap in an 1800 rear, that would get better mileage, raising the travelled speed of the bike for a given rpm. Almost like a cheap overdrive.

 

[07Blackcherry]

I think you have it backwards PaXman

1300 final drive ratio 2.818
1800 final drive ratio 3.091


Honda VTX 1800: review, history, specs - BikesWiki.com, Japanese Motorcycle Encyclopedia
Honda VTX 1300: review, history, specs - BikesWiki.com, Japanese Motorcycle Encyclopedia

 

[PaXman11]

I think you have it backwards PaXman

1300 final drive ratio 2.818
1800 final drive ratio 3.091


Honda VTX 1800: review, history, specs - BikesWiki.com, Japanese Motorcycle Encyclopedia
Honda VTX 1300: review, history, specs - BikesWiki.com, Japanese Motorcycle Encyclopedia

My apology. I've been wrong before. But I'm not POTUS. Maybe his final drives had already been switched by the PO?

 

[07Blackcherry]

My apology. I've been wrong before.

Haven't we all!!! Just wanted everyone to have the correct information, no apologies necessary.

 

[VTX BILL]

Okay, here is what I have found so far.
My speedo has gotten much closer to accurate.
Before it was @10 mph different. Now it is within 3 mph
My fuel has not changed one bit. However if the ODO is based on speedo, then it has changed quite a bit, @ 3mpg better.
Prior to change I was averaging 38mpg
Now I am seeing a consistant 35mpg.
However I am just clearing out my tank with seafoam in it, so that may have something to do with it.
More tanks will tell a better story.
Gear ratios seem different, now I shift from;
1st to 2nd at 30
2nd to 3rd at 40
3rd to 4th at 60
4th to 5th at 70
80 feels like cruise @2500rpm.
Only way to know for sure is to install a tach.
I do feel that the 1800 final drive feels smoother, but that may just be me.

 

[07Blackcherry]

My fuel has not changed one bit. However if the ODO is based on speedo

The odometer is usually off 3-5%, speedo usually off 8-10%. Speedo and maybe odo can be checked with a GPS unit.

 

[VTX BILL]

Okay, here is what I have found so far.
My speedo has gotten much closer to accurate.
Before it was @10 mph different. Now it is within 3 mph
My fuel has not changed one bit. However if the ODO is based on speedo, then it has changed quite a bit, @ 3mpg better.
Prior to change I was averaging 38mpg
Now I am seeing a consistant 35mpg.
However I am just clearing out my tank with seafoam in it, so that may have something to do with it.
More tanks will tell a better story.
Gear ratios seem different, now I shift from;
1st to 2nd at 30
2nd to 3rd at 40
3rd to 4th at 60
4th to 5th at 70
80 feels like cruise @2500rpm.
Only way to know for sure is to install a tach.
I do feel that the 1800 final drive feels smoother, but that may just be me.

THE ANSWER TO THE LONG DEBATED QUESTION
Okay, after 4 tank loads, new plugs and an oil change, I have the final details of changing over from an 1800 to a 1300 final;
1- Gas mileage has gone from 35.5 to 43.5mpg on average.
A- Side road speeds will get me the higher mileage, where interstate still sucks at 30.5 or so.
2- Gear ratio is higher on the 1300, but not by much, though it did get my speedo on target to actual, which I have to believe also changes the odometer. I checked the accuracy of the speedo with both my Garmin as well as a roadside speed checker.

	1800​	1300​
Primary reduction	1.57​	1.935​
Final reduction	3.09​	2.818​
Gear ratio
I	2.35​	1.9​
II	1.48​	1.148​
III	1.11​	0.912​
IV	0.87​	0.778​
V	0.7​	0.697​

source;

Honda VTX 1800: review, history, specs - BikesWiki.com, Japanese Motorcycle Encyclopedia Honda VTX1800: history, specifications, images, videos, manuals. bikeswiki.com

3- Shifting into 5th is comfortably done at 70mph now whereas before it was at around 65 (though again, speedo is almost 7mph different than it was)
The bike seems to run smoother at higher speeds now, and responsiveness at 70+ is pretty astounding.
All in all, I am glad I made the switch. Though I do believe that the improved gas mileage was mostly due to changing out the plugs. They were pretty ratty. I notice a marked improvement after I did.

 

[MB1]

THE ANSWER TO THE LONG DEBATED QUESTION
Okay, after 4 tank loads, new plugs and an oil change, I have the final details of changing over from an 1800 to a 1300 final;
1- Gas mileage has gone from 35.5 to 43.5mpg on average.
A- Side road speeds will get me the higher mileage, where interstate still sucks at 30.5 or so.
2- Gear ratio is higher on the 1300, but not by much, though it did get my speedo on target to actual, which I have to believe also changes the odometer. I checked the accuracy of the speedo with both my Garmin as well as a roadside speed checker.

	1800​	1300​
Primary reduction	1.57​	1.935​
Final reduction	3.09​	2.818​
Gear ratio
I	2.35​	1.9​
II	1.48​	1.148​
III	1.11​	0.912​
IV	0.87​	0.778​
V	0.7​	0.697​

source;

Honda VTX 1800: review, history, specs - BikesWiki.com, Japanese Motorcycle Encyclopedia Honda VTX1800: history, specifications, images, videos, manuals. bikeswiki.com

3- Shifting into 5th is comfortably done at 70mph now whereas before it was at around 65 (though again, speedo is almost 7mph different than it was)
The bike seems to run smoother at higher speeds now, and responsiveness at 70+ is pretty astounding.
All in all, I am glad I made the switch. Though I do believe that the improved gas mileage was mostly due to changing out the plugs. They were pretty ratty. I notice a marked improvement after I did.

Thanks very much to all in this thread but especially VTX Bill for the meticulous work! I was concerned at the beginning of this thread because I bought a X1300 final drive last year fully intending to do the same swap and comfortable in what I thought I knew regarding the gear ratio's. Your work just completely confirmed it. Your a Pro! Many thanks!