why a transmission?

[the13bats]

Im a bit confused and likely this is a very low end question
but where is a transmission needed or a plus,
I am assuming its a gear reduction?

I see home "builds" running say the 79cc or 212cc some will run the thing im calling a transmission, a case with a couple gears and chain then a second chain to their drive sprocket, some dont have the trans they just run the clutch on engine shaft chain to their drive sprocket,

So enlighten me on this,

Thanks
cheers
b

 

[curtisfox]

It is a gear reduction! Like you said, it needs to slow the engine down to get proper power band to move the bike. I think you are looking at China engines they have a built in gear reduction, big gear and small gear driving the big one hence, only one chain to wheel. They also have to very the rear sprocket on the rear wheel some to get the proper ratio for the individual bike..............Curt

 

[the13bats]

Thanks curtis,

Yes and no to your reply,
I do see the gr units on basically all the import bike engine kits, in my mind they have to turn up the rpm on those little 2 strokes to get any power so the gr is a must, it also keeps wheel sprocket size down,

But i was more thinking about my project ( a quadcycle ) and looking at what others have done,
For a long time my plan was a trailer pusher style
I would have 5 wheels but i was going for the feel of the old briggs flyer,

Pretty much any pusher styles i pulled up were on 2 wheelers but it really doesnt know what its pushing,
Most basically look like a mini bike with no front forks attached to what they are pushing,



Most do not have any gear reduction units, just clutch on engine to sprocket on mostly small drive wheels,
All seem to have as much or more speed than im hunting,

then i get a little ADD and OCD, mind engages
I see kits offered to use the 79 or 212 cc engines on a trike,
The direct drive from engine unknown clutch tooth count to a 44 sprocket,

I then consider doing my own version of this, the seat is over the axle on mine but i can mount the engine behind the axle on a plate, chain to sprocket on axle but there is the issue i dont believe a large sprocket on my axle will clear the frame,

So is there a practical way to use jack shafts, or a "transmission" to reduce the size of the axle sprocket yet still get a ratio to push this thing?



Many thanks
cheers
b

 

[curtisfox]

Then you need to go for mini bike gearing, witch is done with #35 chain. most clutches are 10 tooth and wheel sprocket around 60 tooth, divide the teeth 10 into 60 = 60 to 1 . Depends on the wheel size think they have sprockets up 72 tooth.

Look up GoKart supply co's ............Curt