Sprockets and gears

#teeth/#teeth, either or both?

All Shovelhead and other models topics
Post Reply
fjallan
Posts: 26
Joined: Mon May 27, 2019 5:05 pm
Bikes: 1967 FLH
Location: Wa.
Has thanked: 8 times
Been thanked: 5 times

Sprockets and gears

#1

Post by fjallan »

I'm looking for more top speed with less rpms. fresh, stock 74in 67 FLH. I see that when guys are recommending or sharing info about gearing that it is usually displayed in a #T/#T format. for example 24T tranny sprocket / 48T rear wheel sprocket (24T/48T). Does this mean that the bike has now been fitted with a taller tranny gear AND a shorter rear wheel sprocket, or does this mean that the bike has been fitted with EITHER a 24T trans OR a 48T Rear sprocket? I ask because I remember being told that 1 tooth on the tranny is worth 3 on the rear sprocket. I'd like to go longer in first and run at less rpms going 70 mph. I currently have 23 teeth trans and 51 Teeth rear wheel sprocket.



RUBONE
Moderator
Posts: 6155
Joined: Sat Nov 15, 2008 4:09 am
Bikes: Multiple H-D, Ducati, BMW, Triumph, BSA,...
Has thanked: 126 times
Been thanked: 1243 times

Re: Sprockets and gears

#2

Post by RUBONE »

You cannot go smaller on the rear with a stock brake, so unless you change the entire wheel for a later disc set-up you are stuck with 51. Don't try to overgear your bike with that fresh engine or you will ruin it. Lugging it will be the death of it.

RooDog
Site sponsor
Site sponsor
Posts: 1805
Joined: Tue Oct 31, 2017 1:00 pm
Bikes: 1950 Panhead, Resto-Mod
1968 90", 5 Speed Shovelhead,
1984 Custom Built Evo 100" Bagger
Location: Knoxville, Tennessee
Has thanked: 818 times
Been thanked: 693 times

Re: Sprockets and gears

#3

Post by RooDog »

I am going to assume that your 1967 FLH has the stock rear drum brake and you are stuck with a 51 Tooth rear wheel sprocket so there are no other options for that position.
Stop listening to what "they say" and use your own brain. Do the math, the stock 22/51 sprocket combo is a ratio of 2.32, or 2 1/3 tooth on the rear = 1 tooth on the front, but a 24T on the tranny gets closer to a 2:1 ratio. 24 T on the tranny is the largest you may safely run, a 25 will work too, but as the chain wears and flies around the front sprocket it will get into the starter and ratchet housings. You should also be able to run a 24T on your engine shaft, again you are stuck with no options on the clutch shell @ 37 T. So, 24 Engine, 24 Tranny is the biggest you may safely & reasonably go on a stock 1967 FL. But beware, you may not have enough engine to pull those gears if you have a heavily loaded bike and/or a hefty passenger....
....RooDog....

Andygears
Posts: 792
Joined: Tue Feb 05, 2013 12:25 am
Bikes: 1950 panhead, 1999 FLHTCI, 1987 FLHTC custom
Location: Daytona Beach
Has thanked: 113 times
Been thanked: 211 times

Re: Sprockets and gears

#4

Post by Andygears »

All what RooDog said agreed.

What you gain on top you will lose on the bottom (at launch). So, consider what 1st gear is in the trans, 3.00 was stock and will help launch, 2.6? And 2.44 were “Superglide” ratios made for lighter bikes.

Andygears

RooDog
Site sponsor
Site sponsor
Posts: 1805
Joined: Tue Oct 31, 2017 1:00 pm
Bikes: 1950 Panhead, Resto-Mod
1968 90", 5 Speed Shovelhead,
1984 Custom Built Evo 100" Bagger
Location: Knoxville, Tennessee
Has thanked: 818 times
Been thanked: 693 times

Re: Sprockets and gears

#5

Post by RooDog »

Andygears wrote:
Sun Apr 12, 2020 11:38 pm
All what RooDog said agreed.

What you gain on top you will lose on the bottom (at launch). So, consider what 1st gear is in the trans, 3.00 was stock and will help launch, 2.6? And 2.44 were “Superglide” ratios made for lighter bikes.

Andygears
And my favorite with an E start bike is the 5 Speed with a 3.24 low gear, allowing for a way over geared top end ratio....
Works great with a "built" motor....
....RooDog.....

fjallan
Posts: 26
Joined: Mon May 27, 2019 5:05 pm
Bikes: 1967 FLH
Location: Wa.
Has thanked: 8 times
Been thanked: 5 times

Re: Sprockets and gears

#6

Post by fjallan »

is there any gearing changes I can make to cruise easier on the highway I have plenty of low end torque as you know. I'm sure I have some to spare. I'm hitting 2nd gear halfway through an intersection and it pulls for days in 4th uphill. What if I went to a 24 T tranny sprocket without doing anything else? And yes Im aware of the fixed rear sprocket. I always appreciate your input roodog.

pan50head
Posts: 56
Joined: Wed Mar 21, 2007 5:48 pm
Bikes: 1950 FL
Location: Seattle
Been thanked: 3 times

Re: Sprockets and gears

#7

Post by pan50head »

Like probably many Harley riders, I was concerned that the engine was being damaged at higher speeds. At times, the engine would sound like a rattle can. A mechanic I respect told me that a Harley engine can run at 3,000 rpms all day every day with no issues. I counted all my gear teeth, stock engine gear, stock clutch basket, stock wheel and tire size, stock rear drum sprocket with a 24 tooth tranny sprocket. I ran through the formulas and the result was at 70 mph, the engine is turning 3,092 rpms. At 65, 2,872 rpms. At 60, 2,651 rpms. Before I did the calculations, just for grins I put on a 25 tooth tranny sprocket. It ran nice at 70 mph on the flat. If I had to climb a hill, I had to downshift. The engine did not have the power. So, all of this information is worth nothing, but it might be helpful for something.

RooDog
Site sponsor
Site sponsor
Posts: 1805
Joined: Tue Oct 31, 2017 1:00 pm
Bikes: 1950 Panhead, Resto-Mod
1968 90", 5 Speed Shovelhead,
1984 Custom Built Evo 100" Bagger
Location: Knoxville, Tennessee
Has thanked: 818 times
Been thanked: 693 times

Re: Sprockets and gears

#8

Post by RooDog »

It's nice to be appreciated.
I suggest using the 24 T on your Transmission, and then dialing in the final ratio with your motor sprocket as it is easier to access. They are available in 19-25 tooth counts, Tedd's V-Twin lists them all I would start with the commonly available 24 T, and should that prove unsatisfactory, you may go one more tooth in either direction.
BTW: I see no point in running a compensator if you are not in the habit of lugging your motor.
....RooDog....

RooDog
Site sponsor
Site sponsor
Posts: 1805
Joined: Tue Oct 31, 2017 1:00 pm
Bikes: 1950 Panhead, Resto-Mod
1968 90", 5 Speed Shovelhead,
1984 Custom Built Evo 100" Bagger
Location: Knoxville, Tennessee
Has thanked: 818 times
Been thanked: 693 times

Re: Sprockets and gears

#9

Post by RooDog »

Before I did the calculations, just for grins I put on a 25 tooth tranny sprocket. It ran nice at 70 mph on the flat. If I had to climb a hill, I had to downshift. The engine did not have the power. So, all of this information is worth nothing, but it might be helpful for something.
[/quote]

Try an Andrews #1 cam in a stockish motor and see if those hills flatten out for you....

kitabel
Posts: 1021
Joined: Tue Aug 03, 2010 7:10 pm
Bikes: 2008 96" Fat Boy TC
Location: Lynbrook, New York
Been thanked: 144 times
Contact:

Re: Sprockets and gears

#10

Post by kitabel »

Going from one sprocket to another has exactly the following effect: divide new by old to get the change.
From 23 to 24 reduces RPM by 4.35%. Your engine speed, previously 3,500 for example, will drop by (wait for it) 146 RPM. Your MPH, previously 70, will increase by 3 MPH.
You won't feel anything.

The sad, rude truth about tall gearing: the loss of torque in 1st gear is much more painful than the tiny drop in engine speed.

Andygears
Posts: 792
Joined: Tue Feb 05, 2013 12:25 am
Bikes: 1950 panhead, 1999 FLHTCI, 1987 FLHTC custom
Location: Daytona Beach
Has thanked: 113 times
Been thanked: 211 times

Re: Sprockets and gears

#11

Post by Andygears »

Since this post is discussing gearing, let’s consider other factors.

Flywheel weight, stock flywheels or S&S? Heavy flywheels will help the launch but make it harder to achieve top end.
Displacement, 74 inch, 61 inch or 80 or more.
Overall weight, stripped chopper, stock, or heavily accessorized.
And finally, the balance factor on the lower end. There’s a rundown in the Knowledge base about balancing and what factor will achieve smoothness at what RPM. It also mentions that when chasing a smooth ride at speed, tall gearing will often lower the RPM’s to get to a less harmonic vibration point and will “feel” better.
So, unless you want to disassemble your motor and rebalance to a different factor, knowing exactly what type of riding you will do, at what speed, you have to compromise. With the motor in perfect tune, assuming plenty of power to achieve top speed, you need to determine what RPM is smoothest and gear for that RPM at the speed you want to ride most often. Too often the smooth RPM is so low that gearing very high will attain smoothness but wreck the launch and lose “pass a truck” power at speed.
Other stuff to consider to reduce vibration at speed: tire balance, motor/ trans /rear wheel alignment, both chains and sprockets condition, both wheels in line, neck bearings, wheel bearings, swing arm bearings, motor and trans mounting bolts tight.
Engineers try to consider all this stuff when designing a new bike.

Andygears

RooDog
Site sponsor
Site sponsor
Posts: 1805
Joined: Tue Oct 31, 2017 1:00 pm
Bikes: 1950 Panhead, Resto-Mod
1968 90", 5 Speed Shovelhead,
1984 Custom Built Evo 100" Bagger
Location: Knoxville, Tennessee
Has thanked: 818 times
Been thanked: 693 times

Re: Sprockets and gears

#12

Post by RooDog »

Damn !, Andygears covered it all....
And finally: There is no replacement for displacement. One can build up to about 90" engine with no outward signs that it has been "built" so as not to ruin the so much sought after original appearance.
And TORQUE is what it's all about, not horsepower. You need the pulling, cruising, and highway hill climbing torque in the 2-4K RPM range, that is where most non-competition riding is done. An Andrews #1 Cam is high lift, short duration, and satisfies that need in that RPM range......
And with upgraded displacement you can give your left leg, or hand, a rest, and less shifting is required with more power on tap. You can waltz, or you can rack & roll, it's your choice.........
....RooDog.....

fjallan
Posts: 26
Joined: Mon May 27, 2019 5:05 pm
Bikes: 1967 FLH
Location: Wa.
Has thanked: 8 times
Been thanked: 5 times

Re: Sprockets and gears

#13

Post by fjallan »

Great information guys thank you! Im just being lazy here but is the Andrews #1 the same as the Andrews A? I have the Andrews A cam running stock displacement 74" .20 over.

RooDog
Site sponsor
Site sponsor
Posts: 1805
Joined: Tue Oct 31, 2017 1:00 pm
Bikes: 1950 Panhead, Resto-Mod
1968 90", 5 Speed Shovelhead,
1984 Custom Built Evo 100" Bagger
Location: Knoxville, Tennessee
Has thanked: 818 times
Been thanked: 693 times

Re: Sprockets and gears

#14

Post by RooDog »

The two cams are different. The A has longer duration and higher lift. In a Shovel the A's lift of .450 is equal to the #1's lift in a Panny, again @ .450 because of the differing rocker arm ratios. .
Here are all the cam specs one can stand.....

http://nightrider.com/biketech/download ... mSpecs.pdf

Post Reply

Return to “Shovelhead”