need jackshaft explained.

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revolucion

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Apr 27, 2015
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I am a complete noob at this, i am planning my build and i am having a couple issue on understanding how i will start the motor on my boardtrack

the engine is pretty big, predator 212, so i wont need to pedal it whatsoever but would like to have the pedal to start the motor and rest my feet.


i was wondering if someone can explain what the jackshaft does and how the clutch assembly works, and what would be the best way to start the motor. i dont want a pull start.

thanks for your help, i will post the build here soon , still trying to find a hub and spoke size for my 21" motorcycle wheels. i am having trouble finding someone to help finding compatible parts. lots of people have the answer but few speak.
i need to figure out the wheels first to adjust my fork and frame to suit the width. if anyone know what moped hub could fit my 36 spokes dirt bike wheels or where to find appropriate spokes for whatever hub that would work please let me know..

i am stalled and cant just order hubs without really knowing. money is tight.

cheers!
 
Mr.B.

Mr.B.

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Oct 21, 2008
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http://en.wikipedia.org/wiki/Jackshaft

“intermediate shaft in the drive train”

For our bike projects, it’s usually used to make a wide engine aline with a narrower rear axle, while conveniently providing a place to get the drive ratios correct.



Did your 21” wheels come with hubs? If you have the power for it (and 212cc does) you can’t beat motorcycle stoutness!

-Kirk
 
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Mr.B.

Mr.B.

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Oct 21, 2008
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revolucion said:
I am a complete noob at this, i am planning my build and i am having a couple issue on understanding how i will start the motor on my boardtrack

i was wondering if someone can explain what the jackshaft does and how the clutch assembly works, and what would be the best way to start the motor. i dont want a pull start.
Click to expand...
To pedal start you’ll need to have direct drive or some way to lock a centrifugal clutch up during start up. As far as I know no one currently offers a off the shelf part like that.

But if you’re handy it’s possible to build your own- http://motorbicycling.com/showthread.php?t=58662

And there’s always electric start...

-Kirk
 
indian22

indian22

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Dec 31, 2014
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Mr. B good explanations & advice. Yes it can and has been done, but if money is an issue, or time or dependability is important to you & your not a heck of a fabricator with decent tools it's going to be an adventure! I remember a post that Sportscar Pat made that indicated he and his brother had worked on solving the pedal start for their 4 cycle engines & hadn't YET found a viable solution and if you've not discovered their builds yet let me assure you they have formidable skill, talent & dedication to spare!

If money is an issue pull start the 212, if it's not buy an electric start engine...even that will be cheaper than trying to settle the pedal start issue with dependability. Course you could use an electric impact wrench like the racers do... varoom. I tip my hat to you if this is your first motorized bike build. I'd encourage you to read a lot of posts here before getting in much deeper. Hope someone else wades in with kick start advice. Best of luck,Rick C.
 
Mr.B.

Mr.B.

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Oct 21, 2008
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Forgot about the kick start option!

And it has been done here before, worth a search. I recall someone doing it with a small BMX style freewheel on the flywheel side of the engine tied to a stacked chain ring...

-Kirk
 
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revolucion

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Apr 27, 2015
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Thanks guys, good info.

Money is always a problem but i have good fabricating skills,
I build cnc for living, check my site www.revolucionsurfboards.com , pretty cool stuff.
i think i can build this bike. Just need to plan things right.
How does the sportsman bonneville start?
Bumpstart?

Like the briggs bike with the bmx start. Really cool.

My wheels came with hubs but way too big. I would rather use a moped hub.
Smaller, not as wide.

Thanks again and keep the info coming if you have any ideas...
 
indian22

indian22

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Dec 31, 2014
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Glad you found an "Old Guy" to lace them up. Lot of 2 wheel history incorporated into those 3 (Peugeot, Motobecane & Puch) hubs should work out for your build just fine.
Vekst pedal start theory is of interest & hope he gets it up, running & on the market...'cause it would sell, if priced right and dependable. Having a centrif. clutch on the motor drive side for idle, spin up and drive and another freewheel on the pedal side for startup is indeed interesting.

Bonneville's or any bike built with clone type 4 cycles are using the before mentioned starting methods. Competition bikes use an electric or air wrench to spin a hand held drill motor mounted with an appropriate impact socket...which is rather inconvenient for everyday use about town. Pull start & electric are pratical & convenient. Kick starts are practical yet not readily available.

Bump starts aren't used to start centrifugal clutch transport, nor are elevated rear tire wheel spins used because the clutch doesn't engage until spun up to a "designed" speed...2,000 plus rpm quite common on everyday transport, 3,000 plus for high performance & racing. This allows a stationary bike/engine to idle with power train disengaged from the engine. To bump start you need the clutch & drive train engaged at start up, manual clutch is good for this but a single centrif. doesn't readily lend itself to a SIMPLE start, disengage, idle and run solution. Hope this makes sense to you. Happy building! Rick C.
 
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revolucion

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Apr 27, 2015
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Thanks guys, thats great info. i am starting to get it.

i dont understand how is '' Sportsman pedal crank assembly with reduction hub'' that Pat is selling on his site works? is this only to fit the gear of a bigger motor?

also is there a place to get customs spokes? i can lace my own wheels and balance it.

i think so far the simplest system is this one
https://www.youtube.com/watch?v=y8tC1evNNKM
 
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indian22

indian22

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Mr. B in his 2nd. post on your thread shows a nice jackshaft on a bigger engine. Notice that it is mounted on the lower part of the seat tube and above the level of the "bracket shell" housing the pedal bearings and pedal axle. It's a nice looking install that exemplifies how a jackshaft is mounted on many motorized bikes. Notice two things first- #1- The sprocket on the centrif. clutch lines up perfectly with the outside (larger) sprocket on the jackshaft...alignment is perfect. #2- The smaller inside sprocket on the jackshaft is offset so that it is perfectly straight with the rear wheel sprocket. That's one of the things we are looking to achieve on both sides of the bike, perfect chain to sprocket alignment. True alignment of our drive lines is efficient whether we are pedaling or motor driven. A jackshaft is a good way to achieve alignment. It also allows infinite variation of rear drive ratios (options) with 3 spocket calculations being more fun than two & perhaps saving the cost of a custom cut sprocket at the same time! Once I built a couple of bikes the realization hit me that adjustibility of the drive line components was key even with the little China dolls especially when using stock bike frames. Running big tires & wheels without adjustments eats up a lot of sidewall rubber & frame tubes.

The Sportsman design handles the jackshaft function as well, but does it without a separate jackshaft bracket as in the referred to photo. It uses the stock pedal shell 2" bracket, bearings & wide 3 piece crank/shaft/pedals to solve not only motor drive side alignment and gear reduction issues but also addresses the pedal drive alignment and gear reduction issues on the little chain side. It's could be called a "stealth jackshaft" as it dual purposes the bottom bracket for both functions, pedal power & jackshaft. The motor side sprockets are on bearings and connected therefore under engine power the pedals remain stationary until the rider begins to pedal assist. The longer pedal axle & bent cranks also furnish more clearence for the larger engines. Others have also used the bottom bracket concept in builds, yet the Sportsman system is really elegant both in appearence and concept...his price & availability is also reasonable. I machined a similar system a few years back & my time alone cost more than he's charging.

Great system & really cleans up the lines of Pats builds, just because there's a lot going on doesn't mean a bike has to look "busy" & as you know his bikes are clean builds for sure. I'm leaving a lot out about this subject, opening the door in hope that others will share with us their experiences too. Rick C.
 
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sportscarpat

Bonneville Bomber the Salt Flat record breaker
Jun 25, 2009
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Thanks for the compliments, guys! I have put a great deal of time and effort into my drive system. Simple and effective. There are plenty of reasons to use the bottom bracket shaft as the carrier for the reduction hub. Fewer parts means a simpler and more reliable drive, and it removes the need of an engine side idler sprocket which normally carries the chain up and over the frames chain stay tube. Plus, it more closely matches the vintage designs of the motorcycles I use for inspiration. Must have been good reason most manufacturers went to this early design.

Bonneville #6 by Pat Dolan, on Flickr
 
Meano

Meano

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Nov 5, 2011
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Should be able to pedal crank my bike to bad they stop making the manual clutches.
Will be testing it out as soon I have time to finish the brakes.

image-3096663077.jpg
 
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