Engine for a child BMX bicycle???

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WhoDat

New Member
Aug 22, 2012
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Louisiana
Hello, everyone!
My son recently has seen a bicycle with a motor parked by a store and he said he'd like to put a motor on his bike. He is 12 years old and has a BMX bicycle. The bike is not too big but also not a child size. What engine would you recommend for this type of bike and where do I buy it? Also, would it be a very difficult project for someone (me) who's never done anything like that?
Thanksdance1
 

Rocky_Motor

New Member
Nov 14, 2011
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Fort Collins & Boulder
A BMX would require some kind of friction drive setup which may be a perfect way to do things in this case.
Call Duane at http://thatsdax.com/ The website may look unprofessional but everyone on this forum can vouch for his customer service. He may be able to tell you if a friction drive will work with a BMX bike.

Otherwise, the only other option I believe is to buy a pocket bike motor which are 50cc, small only 1-3hp, a gearbox for it, and create your own way to mount it to the bike. This method would use a chain drive instead of friction.

The biggest problem with any of these as that those bikes have no brakes!!! I wouldn't put a motor on a bike that has no brakes.. Although I think a few of them have front brakes.
 

shwnrttr

Member
Dec 2, 2009
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titusville, florida
i wouldnt recommend a engine on a bmx bike,far to dangerous, especially for a 12year old.the smaller the bike the more squirrely it is at high speeds. keep in mind these are not toys. i built a bike for a nieghbor kid,and he ended up wrecking the bike and had to get stitches in his face. all we need is somthing like that to get in the news and ruin the name of motorized bicycles. if you do decide to proceed with a project,make him wear a helmet at least.
 

maurtis

New Member
Dec 14, 2011
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Kyle, TX
Are you looking for gas or electric? Could we get a picture of the frame? Most likely it is a BMX bike with 20" wheels, and a lot of those frames are too small to fit an in-frame motor.

So if you are looking for a front or rear mounted motor, the easiest bet would be a friction drive. A friction drive motor uses a roller attached to the motor itself, and presses down on the tire. It makes for a simpler setup than using a drive chain.

People seem to like these: Bumble Bee Boltons

My first build was a friction drive using a weed eater motor, hand tools, and bar stock from Home Depot. It probably cost me about $120 in parts and the motor was free. It vibrated like mad, but was a fun first build... Mongoose XR-75 build

My son has an electric bicycle that I am thinking about mounting a weed eater motor on the front wheel to get some more top end. So it will be pedal/electric/gas powered ;)
 

WhoDat

New Member
Aug 22, 2012
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Louisiana
Thank you all for the answers. Definetley, safety is first and he will wear a helmet while riding. I will take the picture of the bike's frame and will try to post it here. This bike is somewhat fancier than your regular bmx 20 inch. It has a front and a back brake (on both handles) and the frame is thicker and the bike is longer. I guess, I am still wondering how hard it would be to install something like this for someone who's never done it before.
Thanks
 

MotorBicycleRacing

Well-Known Member
Jul 28, 2010
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Thank you all for the answers. Definetley, safety is first and he will wear a helmet while riding. I will take the picture of the bike's frame and will try to post it here. This bike is somewhat fancier than your regular bmx 20 inch. It has a front and a back brake (on both handles) and the frame is thicker and the bike is longer. I guess, I am still wondering how hard it would be to install something like this for someone who's never done it before.
Thanks
We live in a nanny culture these days and I feel sorry for the kids
growing up today.
just make sure that he wears a full face helmet.

 

moonerdizzle

New Member
Jun 28, 2009
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Cheese head capitol
i wouldnt recommend a engine on a bmx bike,far to dangerous, especially for a 12year old.the smaller the bike the more squirrely it is at high speeds. keep in mind these are not toys. i built a bike for a nieghbor kid,and he ended up wrecking the bike and had to get stitches in his face. all we need is somthing like that to get in the news and ruin the name of motorized bicycles. if you do decide to proceed with a project,make him wear a helmet at least.
BMX bikes are fine at high speeds, ive hit 50 mph blasting down hills on my bmx with no problem and no squirrelyness. and i know when riding dirt trails you can hit speeds of 25-30 mph if your good at pumping the transitions. as long as its not a walmart BMX bike it would be fine. But as for a 12 year old, tell him to wait a few years.
 

Goat Herder

Gutter Rider
Apr 28, 2008
6,237
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I think that really depends on the kid and if he/she has been taught to ride. If they have the aptitude?? Granted just like some adult folks should prolly not be on a motorized bike. Here is a nine year old...http://youtu.be/0MfBDjYReaQ
 

dracothered

New Member
Jul 25, 2012
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Howell, MI.
Yep, all depends on the ability of the kid if they should be riding a gas powered bike. Some should never do it and the only way to know is to try and teach them if they want to ride one. With a helmet of course and done in a safe manner always.

Though what ever is put on the bike it needs both front and bake brakes.
 

turbo1889

New Member
Jun 12, 2012
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NorthWest Montana, USA
You could put a Staton-Inc(.com) axle mount motor kit on it no problem. His axle mount kits are just what they sound like and mount the motor to the left side of the rear wheel axle rather then in the frame triangle.

For a kids bike his 25cc 1.1-hp Robin-Subaru kit would probably be the ticket. It's the lowest powered motor he offers and it's a four stroke so no mixing gas and oil but your kid should still be able to go faster then he can pedal.

The combined weight of me and all the gear I haul on my bike on my daily commute is in the 300-lb range and I'm using his axle mount 35cc 1.6-hp kit and it pushes me along just fine on the flat at a little over 20-mph when I don't pedal at all and running both the motor and pedaling in top gear I cruise at about 25-mph.

Se no reason why the Staton 25cc axle mount kit with a 13 or 14 tooth drive sprocket on the gear box wouldn't push your considerably lighter weight son and his bike down the road at similar speeds.

Here is a direct hot link to the axle mount kits I'm talking about:

http://www.staton-inc.com/store/cat..._Gear_Chain_Drive_Engine_Motor_Kits-14-1.html

The speed calculations on his standard list are calculated for a 26" wheel but if you would just simply use his provided note fields to explain that your going to put his kit on a 20" wheel BMX bike and you want the alternate mounting bracket for the smaller wheel size and a 13 or 14 tooth drive sprocket to compensate for the smaller wheel size. His kits are among the best quality and are very reliable which is a major concern for me as a daily commuter.

Don't know if that would work for you or not but I suggest it because his axle mount kits don't require frame space for the motor and have been used on wheel sizes all the way down to 16" and he already has alternate brackets in stock that hold the engine up higher for ground clearance on the smaller wheel sizes and all you have to do is ask in the notes and he sends you the alternate small wheel bracket.

Obvously you could also put a 35cc size 1.6-hp four cycle motor kit on your kids BMX bike like I have on mine if you think he can handle the extra power and since he is (presumably) a lot lighter then me and my gear he could go faster then I do with a bigger drive sprocket. You could go with a more powerful two cycle motor kit as well but the four cycle kits are so nice not having to mix gas and just being able to fill up anywhere.

Another potential nice thing about the staton axle mount kits is that you as the father can adjust how fast he can go under motor power just by changing out the drive sprocket on the gear-box. With a 20" wheel the smallest size 10 tooth sprocket will only let him go about 17-18 mph when the motor is wide open throttle at its highest RPM and if you put a 16 tooth sprocket on that motor RPM regulated top speed jumps up to 27-28 mph with a 20" wheel size and all the sprockets inbetween adjust incrimentally assuming the motor used has the power to spool all the way up to its full RPM pushing the weight of your kid and his bike.
 
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maurtis

New Member
Dec 14, 2011
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Kyle, TX
I am actually surprised at the concern over a 12 year old on a motorized bicycle. I got my first motorcycle, a 1980 Honda z50, on my 7th birthday. No helmets, no MSF course. Rode it about 50/50 street and dirt around the neighborhood. How many people think you should have to be over 12 to ride those little 50s? Around that age I inherited my brother's Suzuki DS80 2 smoke. That was a completely different beast than the little Honda!

But I do agree that he needs to make sure the bike has good front and rear brakes. I have an excellent front brake for my HT build, it is sitting in a box waiting to be laced up, LMAO. Yeah, I really do need to get that done...
 

Saddletramp1200

Custom MB Buiilder
May 7, 2008
1,451
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Houston, Texas
Mom was riding with me in her belly. Got my first Mini bike @ 6. Daddy better watch that kid like you breathe! Put a carb block on it to slow him or her down. We need to know what kind of motor you get :)
 

WhoDat

New Member
Aug 22, 2012
4
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0
Louisiana
Ok, finally took the picture of bike, attaching it to this message. What are your suggestions for an easy way to make this bike motorized?
Thanks
 

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JonnyR

New Member
May 13, 2012
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ronkonkoma, new york
welcome to the forum this is a great place if you need MB advice

my cousin got his kid a honda 50 when he was 11. age has nothing to do with it now hes 12 and rides like a semi pro and is looking for more power just remember he needs a full face helmet i have a scar on my chin from 14 stitches and i was wearing a DOT shorty helmet it could have been worse helmets save lives .
i think its great if he wants a MB it will teach him alot about engines and bike maintenance.
the friction drive is the best bet for him to start with the BMX bike frames are kinda small for in frame and i agree thatdax.com is the best choice for it when he gets bigger you can transfer it to a bigger bike or build him a in frame.
 

4you2eat

Member
Oct 27, 2012
101
12
18
Spring Texas
I did one for a kiddo on a 20" bike. It required a good bit of frame mods. IMO the friction drive mount on such a small frame would be unstable with the weight above the tire. Good luck and get the kiddo a helmet pleeeeeze