Building a Motorized Scooter/Bike

carl_baron123

New Member
Jan 12, 2009
12
0
0
Australia
Hey, I am new to the foruma and the art of motorizing bikes but I am very interested.

I am going to build a powered scooter or bike but am unsure which type of engine I should use. I was thinking along the lines of either a whipper snipper (weed wacker) or chainsaw engine and I am still deciding whether to use a chain drive or spindle drive. I was thinking about a spindle drive with springs attached to a foot pedal. I really want to use an offroad style scooter that I have had from a kid. It has 16" wheels. I also have an old greenfield vertical shaft mower but it seems to be useless to me unless I can make a 90 degree thing which I can't. A chainsaw motor should go well with a chain drive with its centrifugal clutch. I might pick one up today in town. Any ideas for me. I do not know how to attach a throttle but I have a honda four wheeler that I can use for parts. Could I use a thumb throttle off that? I don't know how I would use it.
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,574
156
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Welcome to the sport.

The most important thing you need to do is to come up with a working gear ratio, especially with a high-winding engine. You will probably end up using two jackshafts unless you find a gear reduction box.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
the friction drive spindle is by far the easiest to build, but for off road it would be the least efficient. For the engine chain saw and WW are pretty good sources. The WWs are the easiest to find and the least expensive of the two.

For a scooter design you might even consider the horizontal shaft cultivator or generator engines. With a scooter the engine will be your only source of power. With a bike you have the pedals to help you along in a pinch. That's why I prefer the bike.
 

carl_baron123

New Member
Jan 12, 2009
12
0
0
Australia
Ok thanks guys, I was thinking that the spindle would be easiest to make but it would not suit my conditions as I am completely surrounded by dirt roads. Can someone explain the gear ratios and what would be optimal for say a weed wacker chain drive on a scooter? I don't really understand that part, and what is the point of having a jackshaft? That just looks hard to make...!
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,574
156
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Sure jackshafts seems like a pain, but you need about 19:1 gears or more to maximize engine efficiency. I don't believe there are many gear reduction boxes for weedwhackers and chainsaws. With a 5:1 box you'd just need a 10tooth/40tooth sprocket combination to get 20:1. Without the reduction gearbox, you'd need 10t/40t, 10t/40t and 10t/13t, you'd need two jackshafts to arrive at 20.8:1 ratio.

IF you used just the 10tooth/40tooth, your bike's not going anywhere when you gas the engine.

You WILL burn the clutch.
 
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carl_baron123

New Member
Jan 12, 2009
12
0
0
Australia
what about say a 10t to an 89t rear? will that burn the clutch? I have seen heaps of pictures with the front sprocket running directly to the rear with no jackshaft and they only look to be ratios of say 6:1... Is it really necessary to have a jackshaft? Baron.
 

comfortableshoes

New Member
Jul 22, 2008
606
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Beverly, MA USA
what about say a 10t to an 89t rear? will that burn the clutch? I have seen heaps of pictures with the front sprocket running directly to the rear with no jackshaft and they only look to be ratios of say 6:1... Is it really necessary to have a jackshaft? Baron.
usually those scooters that are going direct to the back tire/gear have a gear box that is attached to the engine, it doesn't look like anything because it's made to blend in with the engine.... I have a go ped type scooter and that is what it does...

As for using a chain saw, with out welding on a sprocket the gear/sprocket that drives the saw blade won't work for the chain of a bike/scooter.

I agree with deacon on this- the WW is by far the least expensive option. I also find WW very easy to modify and mount..cs.
 

carl_baron123

New Member
Jan 12, 2009
12
0
0
Australia
usually those scooters that are going direct to the back tire/gear have a gear box that is attached to the engine, it doesn't look like anything because it's made to blend in with the engine.... I have a go ped type scooter and that is what it does...

As for using a chain saw, with out welding on a sprocket the gear/sprocket that drives the saw blade won't work for the chain of a bike/scooter.

I agree with deacon on this- the WW is by far the least expensive option. I also find WW very easy to modify and mount..cs.
Yeah ok, that sounds good. I think I will go with the WW motor. But I am not sure whether the motor will still turn when I am idling or will it stop completely like a chainsaw with a centrifugal clutch. Any ideas?
 

5-7HEAVEN

Well-Known Member
Aug 2, 2008
2,574
156
63
The engines with 6:1 ratio are large 4-stroke engines who peak at 3600 rpm. They don't need stiff gears because they peak at 3600-4000rpm.

If I were to install a spindle-type friction drive with no clutch, I'd fab a hinge to lift the engine off the tire at a dead stop..bld.
 

comfortableshoes

New Member
Jul 22, 2008
606
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0
Beverly, MA USA
5-7Heaven- *slap forehead* duh gravity clutch

Check out Deacon and my weedwacker build threads, we both use hinges on our builds. I use a series of pulleys and a brake lever to lift mine deacon makes a long lever from steel for most of his builds...

If you search the forum for MadWagon you'll find my build and lots of pictures, also in my signature I have a link to flickr and hundreds of pictures of my builds.