Transmission dilemma, need your real life experience?

Just to let you know,
the only reason I go for a chain drive, and not a CVT, is because of better MPG, due to less losses with a CVT.

on a scooter, a CVT allows for faster acceleration for a while, but then becomes ridiculously slow in acceleration, partly due to CVT friction in the belt.

A chain has virtually no friction, so there's more performance out of it.
And for a 50cc it is welcome!
Less CVT friction will allow higher top speeds, and lower gas mileage, and less wear (a belt needs to be changed every 4-6k miles).

So, with the right gearing, you can create a bike that accelerates just as fast as most cars from a red light, and still rides quite fine up 'till 30 something MPH.
Or put a tall gear on it, and pedal assist to accelerate, and gain greater top speeds than a scooter can have (est. 50-55MPH max),, or use the tall gear to ride normally, and get lower RPM's, thus have better MPG.

Russell's Integrated motor mount and jack shaft is probably the most elegantly simple & inexpensive jackshaft setup I've seen, aside from the pipe & plate here's a basic parts list;

http://www.amazon.com/gp/product/B000WPU3FU sealed bearings $5 x2

http://www.bmikarts.com/58-Keyed-Shaft_p_1047.html 5/8" keyed shaft $12

http://www.staton-inc.com/store/pro...cket_13_14_15_tooth_30mm_x_1_0_OD-529-20.html $14.30 5/8" ID freewheel adapter $14.30

& add whatever 5/8" ID sprockets you choose, commonly available they're usually around $5 or so - I liked it so much I adapted the concept for my recumbent build. While perhaps not applicable for your project, I was overjoyed to find that w/the threads dremeled smooth, the sealed bearings pressed into the extra bottom bracket like it was made that way;



tadpole jack shaft & freewheel demo vid

Food fer thought

CVT's aren't loud at all. They just eat performance.
A CVT costs money, and is hard to install on a bicycle, unless you do welding.
To get better torque, just change the rear sprocket from 41 or 43T to higher. Usually 51T's are the highest, however you may be able to do wheelies, but you won't go very fast with it, unless the engine's screaming on top of it's 'lungs', or pistons, so to speak ;-).

Moto pope said:

My model are the Pope, Harley, Indians, etc. of that era. I want it to look as "period correct" as practical while using modern running gear for relialibility. With this in mind,

I finally chose a Lifan 79cc ohv verticle cylinder. With some work, I think I can make it appear vintage.

I need you guys to help me decide between a Q-matic, cvt unit, or jack shaft (either production or DIY).

Click to expand...

CVT won't work well with that low powered motor.

Jack shaft is the only way to go to look right, a Q Matic is expensive and ugly.

Also check out culvercityclassic GC 160 CVT and jack shaft builds.

Check out Motomagz cool bike which uses a similar 98 cc Lifan and jack shaft
from www.affordablegokarts.com

It's cool to be able to use the bike's gears if it has any!
If it doesn't, then you'll depend on the sprocket you install, and are limited to that one.

For instance, install a 51T, you'll have fast acceleration, slow speed, low MPG.
Install a 41T, and you'll have moderate everything,
Install a 36T, and you have slow acceleration, but great MPG, and great top speed!

speed and torque will always depend on the gearing and the engine's rpm range. I have a 98cc Lifan with a max rpm of maybe 5200, and with that in mind I have geared it to top out around 32. I expect this gear ratio to give me plenty of torque for hill climbing. with your engine, I recommend similar gearing being that you are going for more torque. My final ratio is 12.44:1, and I went with a custom made jackshaft designed by forum member culvercityclassic. As far as period correct goes, I would say the integrated motor mount/jackshaft is as close as you will come to period correct without buying or copying the real thing. Just my thoughts. Now back to gear ratios. Here is how I achieved my ratio. I went 11t on the clutch (which is on the crankshaft, the qmatic has the clutch on the second pulley so its a bit different), 28t on the jackshaft input, 9t on the jackshaft output, and 44t on the rear wheel. Thats 11-28-9-44. Just remember, with the fact being that a 4 stroke has no built-in gear reduction, the sprocket on the rear wheel is not the only one that is important. You will need to figure out what gear ratio you want and figure out what drivetrain you want to use, then select the appropriate size sprockets or pulleys to achieve your desired ratio. Its very important to know what your max rpm is (your engine most likely has a governor, removing it will change the max rpms and is highly recommended), and to know what gear ratio will give you what top speed. A lower top speed will give you more torque.

The guys here are giving you lots of good advice, hope you're on the road soon.

Ive made 3 jack-shaft drive lines with this.

http://www.niagaracycle.com/categories/torker-tri-star-3-speed-coaster-brake-hub

I use this sprocket

http://www.fancyscooters.com/item00298-scooter-part-sprocket-type-i-55-12-mm-12-tooth.html

With this gearbox

http://www.partsforscooters.com/transmission?sc=32&category=132677

The shifter as-jack-shaft gives me super duper hill climb power as a 40 mph cruise speed at around 6000 rpm+, comes with the hardware too.

Fear-not the hub... it can take big power as a jack-shaft when you connect it to the 5-to1 tranny. Thousands of miles on them and they just seem to work better and better as time goes on...

P.S. Look closely at the sprockets (plural!) on that nexus hub.