Sprocket Question/ Opinion

[dukekleman]

I agree. Rod to stroke ratio is critical component of a build. Due to the increase in overall engine height which affects the center of gravity characteristics of a motorcycle, it's often sacrificed in engine development to a point...The longer rod greatly affects piston speeds and piston stability. I've seen it time and time in development. It's my opinion that a longer rod is better overall.

[Carl Olsen]

I have BDL make a special belt drive that is higher ratio on the engine and the clutch, this setup allows you to cruise at 65-70 with a stock 22 tooth trans sprocket so your speedo reads correct. It is enclosed in the primary cover, so it does not detract from the original looks, and we make a modified breather tube that reroutes the chain oiler to the rear chain. Basically, set it and forget it, no need for ever adjusting the primary, so you never have to worry about readjusting you clutch and shifter. All my bikes are set up with this drive mechanism and a competitor clutch for ease of maintenance, smoother ride, and lower RPMs on the engine for longer life. This is real world stuff as most of you AMCA members know that we ride our bikes and build them that way for our customers so they can do the same.
Carl

[BigLakeBob]

Carl, do the BDL belt drive units you have special made come with either a tapered ID or a splined ID front pulley?

Thanks.

[Carl Olsen]

Both, they are $500 including the breather tube plus shipping.
Carl

[kitabel]

A belt drive isn't magic, just another way of adjusting the primary ratio:
# teeth on the clutch shell / # of teeth on the engine pulley.

Just 10 times as expensive.

[chuckthebeatertruck]

Having been on several road runs with the Olsen’s, yes, their bikes work and yes, they ride them with aplomb.

[chuckthebeatertruck]

I'm curious. How much would changing the balance factor to smooth out the higher RPMs effect the ride at city street speeds?

You won’t likely notice. Unless you have buddies who only insist on running 75 plus, you generally don’t need to deal with higher balance factors. Most big twins are super happy between 45 and 70mph with a 50-55 percent factor.

For most riders, properly tightening mounts followed by good, fresh tires and capped by a belt drive primary will make the biggest difference across the widest range. Next best thing is sheepskin under your butt, gel in your insoles and good elk skin ropers on your hands. Put in a set of ear plugs on top of that and suddenly, a lot of secondary vibration and noise disappears.

To tires, I have often solved bad vibe issues for gents simply by spooning on fresh, soft tires. A surprising number of riders don’t put enough miles on to wear out tires and when I find tires with date codes from the 20th century, there’s a good chance the bike rides poorly too. Second big thing is a total lack of swing arm maintenance on Harley. I swear they turn into rigids if you don’t actually service them Once a decade or every 10k miles, which ever comes first.

And if you’re afraid of belts shredding on the road, please know you can replace one pretty easily on side of road. If you can’t turn the belt roughly 90 degrees then it is too tight. That looseness means you can oft work a replacement belt on just by letting it sit in the sun an hour.

[otis71]

Just curious if anyone has this thought process? I’ve been told that it’s best to step up the transmission sprocket rather than the engine sprocket so the transmission doesn’t spin as fast. Doesn’t seem an issue either way, just a thought.

[T. Cotten]

Just curious if anyone has this thought process? I’ve been told that it’s best to step up the transmission sprocket rather than the engine sprocket so the transmission doesn’t spin as fast. Doesn’t seem an issue either way, just a thought.

We are all armchair-engineers, Otis!

Theory is easy.

Seat-of-the-pants results however,... May vary.

....Cotten
PS: In spite of higher modern highway speeds, I still advocate gearing low. Use it, or you will never know the powerband you are missing.

SPRKTTBL.jpg

[Steve Slocombe]

Just for completeness, here are the ratios for the 3 speed VL transmission. Stock drive sprocket was 23 tooth (bizarrely 22 after the more powerful 1934 motors), clutch 51 tooth, countershaft sprocket 28 tooth, rear sprocket 51 tooth, to give 4.039 overall gearing. With the 25 tooth 'racing' drive sprocket this became 3.716 and with my super tall 27 tooth down to 3.440. This gave 103 mph on an airfield run on 19 x 4.00 tyres, but you could really feel the gap between second and high, and of course riding in town was not great with that high first gear. The VL is 220 pounds lighter than a heritage softtail classic, and maybe 150 pounds lighter than a sixties FL, but still good for highway speeds today. They were designed for dirt roads, so probably under-geared, and will take a tooth or two extra than the stock drive sprockets on these new-fangled paved roads.

[dukekleman]

It's my opinion that a Direct drive design transmission, as these are, benefit from a medium. From that I mean a 23 or 24 (24 if the motor pulls it with out lugging). Then a 24 or 25 at the engine sprocket. The reason I like these combinations are as follows.
1) The rpm input through the main shaft and two the countershaft is lowered. This lower rpm is beneficial in an overlooked component of "shifting". It aids in moving the heavy shift dog axially on the shafts through heavy weight oil. It's my opinion that they shift smoother.
2) The added benefit for starting the vehicle. When you run the combination or direction I'm referring to on the engine sprocket, you change the "Kick start" ratio. This changes the crankshaft input towards connecting rod/piston rotation. This helps with starting. It aids with different compression ratios and ignition systems. I still prefer point ignition but those that opt for electronic ignition can benefit from this.

Gearing is obviously all about mechanical advantages. Each rider style, sidecar , no side car, etc matters. Choose wisely because incorrect gearing with improper rider gear selection can be very harmful to the lowered end and the pistons of the engine.

[kitabel]

A larger engine sprocket increases leverage for kick starting (less effort), but the engine also turns over more slowly.

[dukekleman]

The engine sprocket which is normally your drive sprocket in gear ratio formula, now becomes the driven sprocket in the formula and definitely aids in starting and piston motion...

[Carl Olsen]

Just 10 times as expensive.[/QUOTE]
Tell me where you can buy a new chain drive primary setup for $50 (10% of $500 for a new belt drive) and I will buy as many as I can get my hands on. You mentioned changing to a 5 speed, that would certainly cost way more than a belt drive. Come out and ride with me on one of my long trips on a knuckle and put up or shut up.