The Bronco

#1
It was a Garelli Bronco.

Plans are to make the bike into something similar to the attached pic.


1. First question for you guys is whether you'd keep the jackshaft setup or flip the swingarm and run a single chain on the left.

Personally I prefer the single chain look on a bike like the example.

2. Planning to mount a single 125cc pitbike shock in the rear vs the dual shocks. Any reason why not?

3. Since this was a Garelli Bronco and parts don't exist in Canada what would you recommend for brakes? Disk setup or would I just need to find the right size shoes from another bike?
 

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DaddyJohn

Active Member
#2
Only problem with that scheme is the big wheels on your bike ensure that your gearing will be way off.

You'll need to get a new rear sprocket that's only slightly smaller in diameter than your rear tire. :D
 
#3
I like your vision. You don't need to flip the swing arm though do you? Just the rear wheel? I'd ditch the jackshaft and run a TAV2 setup. You might be able to get away with that single sided with some careful planning. Plenty of torque and speed...
 
#4
Only problem with that scheme is the big wheels on your bike ensure that your gearing will be way off.

You'll need to get a new rear sprocket that's only slightly smaller in diameter than your rear tire. :D
Thanks for the reply. That is reason enough to stay with the jackshaft setup then I guess. I don't like the look of massive sprockets, especially on a 10" wheel.

The swingarm would have had to be flipped only because the one side has a slot to hold the brake drum from rotating.


If I keep the jackshaft I guess I'll just flip my clutch so the chain runs on the inside. The current setup took up too much space which was my initial reason for wanting to go single chain.
 
#5
Ok so the old jackshaft is all welded up on both sides. I thought only one side was welded until I cleaned the greasy dirt off today.

If I chop it up I'd have to keep one of the welded sprockets, either the 26t input or 10t output.

Calculating it the way it sits I'll get a blistering max speed of 17.4mph. Unacceptable.

If I calculate it with the 10t clutch (still new, won't be changing this) and the current 33t wheel/axle sprocket I'm looking at around 45 mph according to the calculator. That's more than enough for a bike that's going to be riden mostly off road I think....

That means back to the original idea of flipping the swingarm/rear wheel.

Before I do that I'm curious if I'll have enough torque to ride around in a decent manner. I can always cut a ring or two off my clutch spring to increase its engagement Rpm.



Thoughts?
 

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#6
Please excuse the back and forth decision making. I've been into bikes since I was a kid and have had a few but this will be my first "build" so I'm sure there will be a bunch of that.

I rebuilt a crashed pitbike a few months back and got the itch to keep tinkering. Sold that thing before I even got to ride it.
 
#7
Ok so the old jackshaft is all welded up on both sides. I thought only one side was welded until I cleaned the greasy dirt off today.

If I chop it up I'd have to keep one of the welded sprockets, either the 26t input or 10t output.

Calculating it the way it sits I'll get a blistering max speed of 17.4mph. Unacceptable.

If I calculate it with the 10t clutch (still new, won't be changing this) and the current 33t wheel/axle sprocket I'm looking at around 45 mph according to the calculator. That's more than enough for a bike that's going to be riden mostly off road I think....

That means back to the original idea of flipping the swingarm/rear wheel.

Before I do that I'm curious if I'll have enough torque to ride around in a decent manner. I can always cut a ring or two off my clutch spring to increase its engagement Rpm.



Thoughts?
As I said above, with those diameter wheels and mostly off road riding, a TAV2 is really the way to go. plenty of torque and speed for the same price as a clutch and jackshaft...
 
#8
As I said above, with those diameter wheels and mostly off road riding, a TAV2 is really the way to go. plenty of torque and speed for the same price as a clutch and jackshaft...

Would the 10t clutch that I already have and 33t sprocket (can change) not work well enough?

Speed calculators suggest it will, but will it have enough torque with a 180lb rider to be rideable on a trail?

Torque converters around here run $299Cad minimum plus the bulk doesn't really flow with the minimalist look I'm going for.
 
#9
Would the 10t clutch that I already have and 33t sprocket (can change) not work well enough?

Speed calculators suggest it will, but will it have enough torque with a 180lb rider to be rideable on a trail?

Torque converters around here run $299Cad minimum plus the bulk doesn't really flow with the minimalist look I'm going for.
Speaking from experience, you'll be a lot happier with a TAV. The China copy of the TAV2 is more than adequate(I hate to admit this right now). Check out Amazon or Ebay. Should be able to score one for $60 US or so. I guess you need to decide if you want a trail capable bike or an aesthetically pleasing bike?
 
#10
What part of my potential idea makes it not trail capable? Not asking sarcastically, asking to learn. As you know, a speed calculator might indicate one thing but real world experience could be completely different.

I have two new pillow blocks here too so I can still go with another jack shaft setup.

It most certainly could be my lack of experience but I really dislike the idea of running my bike on a belt.

Realistically the main trails I'd ride around here are more or less flat. I would probably do most of my riding between 20kmh (12.4mph) and a max of 60kmh (37mph).

I truly appreciate your replies.
 
#11
A TAV2 (CVT) helps optimize the tourqe multiplication through out the engine's whole power curve. As applied gearing changes with engine speed. That doesn't mean that with the right gearing from a clutch and jackshaft setup it can't be an effective trail bike. All it means is that it is a constant fixed gearing. So really only can be optimized for one part of engine's power curve. A CVT just allows for more tourque optimization when speeding up and slowing down on inconsistent terrain. Hope that helps explain why people are suggesting a TAV2. In the end it is your bike and you should do as you please and to fit your wants and needs. :D
 
#13
You are welcome. I can understand wanting to avoid the bulk of the TAV2. I am currently running a clutch and jackshaft on my trail bike and I can make it up steep hills easily, I'm around 170 pounds, but I have a pretty numerically low gear ratio. So I top out at about 22 mph or 35 kmh.
 

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