4 Speeds and Gear ratios

[drivermark]

Let's see if I can word this in a way that makes sense.

First a little background: I have an 85 Softail that at the moment the transmission is out and opened up. I have been wondering if it would be worthwhile since I am already this far into it to change the first gear to the lower FL ratio 1st gear and then either use a larger trans sprocket or smaller rear wheel sprocket to lower the cruising speed RPMs without losing too much on the bottom end.

The reasoning (in my head anyway) is that everyone I ride with has a 100 ci engine or larger. My thinking is that this type of change would make it easier for the little 80 in. I got to keep up with the bigger engines in the newer bikes I ride with.

Now the question I have is: Is this feasible, or even possible, OR... Do I just have my head in my ass?

[Dragstews]

Gotta have a strong motor to pull tall gearing ...

[drivermark]

It's built up a little from stock but it's no racing beast. 10:1 wiseco pistons, EV27 cam, S&S Super E, nothing spectacular but a little more oomph than stock.
Not really try to jack it up too much, just really trying to drop cruising rpm a bit. Chasing all the other guys running @ 85-90 she just seems too be wound up a little high.
was just thinking of a 24 or 25 tooth trans sprocket OR a 48 or 49 tooth rear sprocket. Nothing too wild

[JBinNC]

23/48 is definitely doable. My FXWG, with box stock evo is running that ratio, with the FXE gearset.

If you make the front sprocket large, the chain will eat into the inner primary and starter gear housing, try as you might to keep the chain adjusted.

Jim

[drivermark]

Thanks Jim, good to know.

[jdmboyd]

Jim's right, it's bound to chew things up.

That said, I'm a dope and running 26/45 on my '80 FLH. Not beating anyone off the line but high speed is nice w/o the motor staining and feeling like it's ready to explode.

At some point I'll need to replace the inner primary and starter gear housing as Jim says. I'm liking it now, though.

Here's a crazy thought: Does anyone build a planetary OD in the rear wheel? I know, lots more complicated than just having a 5th gear that's OD, but curious.

John

[drivermark]

I just happened to read in Easyriders Tips and Tricks #1 an article about that (the chain chewing up the starter gear housing) called "How not to Score" you can find a PDF at the link below the article is on page 129 I believe. It has a tip on how to avoid that.

https://drive.google.com/file/d/0B4sSBYkFYLhvUTRKSXFEVmVJY28/edit?resourcekey=0-KTUQG_Gj5vnNgJyN2bCGTQ

[Tattooo]

The biggest problem with larger sprockets is O ring chains............. I will NEVER run one........

[confab]

I used some silicone and glued a thick, plastic, case saver to the bottom of the starter area on the inner primary.

They work pretty well.

[drivermark]

The biggest problem with larger sprockets is O ring chains............. I will NEVER run one........

What's the deal with the O-ring chains? Are they bigger somehow (I've never looked at one)

[TriNortchopz]

Harley-Davidson Big Twin Gear Ratios

To use this Chart
This Chart gives over-all gear ratios (in 4th gear) for all 1936-* 4 speed big twin transmissions.
"Motor-Trans" are engine & countershaft sprocket tooth counts, respectively.
Assumptions made are: rear tire diameter: 26", std. clutch drum: 37 tooth, std. rear sprocket: 51 tooth.

http://victorylibrary.com/tech/gr-bt.htm

reference for assumed 26" tire diameter:

Common Motorcycle Tire Sizes Chart

The following chart shows some common tire sizes, including their width and the diameter.."

https://www.lowbrowcustoms.com/blogs/motorcycle-how-to-guides/motorcycle-tire-sizes-comparison-chart

a calculator:

Calculate RPM For A Given Speed In Top Gear

https://bakerdrivetrain.com/pages/calculate-gear-ratios-on-your-motorcycle-rpm-vs-speed

[Tattooo]

What's the deal with the O-ring chains? Are they bigger somehow (I've never looked at one)

Yes sir they are wider....... Hell they might even be a little taller I've never measured them to see............ Plus they say to clean and oil them........... If you do that to a regular chain they will also last longer............

[drivermark]

Yes sir they are wider....... Hell they might even be a little taller I've never measured them to see............ Plus they say to clean and oil them........... If you do that to a regular chain they will also last longer............

And they cost more (which is probably why I've never even looked at one)

[Rich54]

I realize this is an older thread but I also have a 1984 softail with a 97 inch evo. I currently switched to a brute 2 extreme belt drive for a shovelhead. That changed the primary drive ratio from 1.54 to 1.48 to 1. I was also thinking of running the flh ratios to give me a better first gear ratio and then use the rear sprockets to adjust my final drive ratio.

[JBinNC]

I realize this is an older thread but I also have a 1984 softail with a 97 inch evo. I currently switched to a brute 2 extreme belt drive for a shovelhead. That changed the primary drive ratio from 1.54 to 1.48 to 1. I was also thinking of running the flh ratios to give me a better first gear ratio and then use the rear sprockets to adjust my final drive ratio.

The 3.0:1 FL first gear ratio makes the 1 - 2 upshift harsh. If you are contemplating this change, you will probably like the Andrews 2.60:1 first gear better. In your transmission, you will have to change the c'shaft second gear to the older 1.82:1 to match the first gear cluster. I have been swapping in the 2.60:1 first gear on pretty much every FL transmission i rebuild, and I haven't had a complaint yet.

Jim