I really want to attach an engine to my BMX...

[CrimsonPrince]

I have a standard Fit Augie BMX and am looking to motorize it. My options are to get an electric front hub (nearly $200), or, with YOUR help and insight, I can (preferably) put a mini/pocket motor on the bike. How do you guys think I cna go about doing the pocket engine? Is it even possible? Thanks in advance.

 

[5-7HEAVEN]

Your mid frame doesn't seem to be big enough for any engine.

Best bet is a front or rear friction drive engine.

You can buy the friction drive kit with or without engine.

The pocket bike engine is quite powerful and bolts right onto the friction drive housing.

I don't know how dependable this engine is.

 

[CrimsonPrince]

The next question would be do you want to keep the pedals? Finally how do you feel about a rear rack mount?

HI Jerry! Yes, I'd like to keep the pedals, if possible. I wouldnt be opposed to a rear rack mount, but I'm really trying to avoid a friction drive setup, due to the fact that my tires are pretty pricey and friction drive can really wear out tires faster. I was thinking about the electric hubs, but they are upwards of 600-800 dollars after I did a bit of research

 

[CrimsonPrince]

Your mid frame doesn't seem to be big enough for any engine.

Best bet is a front or rear friction drive engine.

You can buy the friction drive kit with or without engine.

The pocket bike engine is quite powerful and bolts right onto the friction drive housing.

I don't know how dependable this engine is.

Nice, Im in Honolulu too!

 

[5-7HEAVEN]

Nice, Im in Honolulu too!

How's the Covid lockdown affecting you?

It gives me more time to build my bike.

 

[5-7HEAVEN]

HI Jerry! Yes, I'd like to keep the pedals, if possible. I wouldnt be opposed to a rear rack mount, but I'm really trying to avoid a friction drive setup, due to the fact that my tires are pretty pricey and friction drive can really wear out tires faster. I was thinking about the electric hubs, but they are upwards of 600-800 dollars after I did a bit of research

Yes, friction drive(FD) eats tires.

My first mbs were FD's.

Front hubs would be the simplest.

Front engine chain drive would make more sense.
Looks weird, but better balanced.

There are no kits for front chain drive, so you'd have to
engineer it yourself.

You could research the forums; it's been done before.

 

[CrimsonPrince]

How's the Covid lockdown affecting you?

It gives me more time to build my bike.

Not really afecting me much, man! I wanted to work on a build for my bike, but I dont know if I can build around my small bmx frame dimensions. I would prefer not to modify the frame and just buy and engine that works for the bike

 

[CrimsonPrince]

I've seen several BMX rear mount builds using China girl kits with a left side rear wheel sprocket.

Some BMX frames will allow you to squeeze a China girl into them but most of them will require the frame be modified by redesigning, cutting, fitting and welding.

View attachment 105675 View attachment 105676

THanks Jerry! THat first idea is gold! Fitting the China girl onto the extended seatpost seems like it would work for my bike actually. THe guy in the video has a 20" wheelset with, what looks to me, a 20" toptube length (small like mine). Got any more material on how to build one of those?

 

[5-7HEAVEN]

You do realize that mounting an engine on the seatpost transmits constant vibrations literally right up your butt!

I'm not sure any person can handle that for long.

What I'd suggest is an engine mounted on the left side rear axle.

There is a kit offered by Staton-inc.com

It uses any engine using a 76mm clutch.
Engines that can be used range from a 1.25hp Subaru to the powerful 4.5hp CY460 engine.

A compact transmission connects to a short chain to a driven sprocket on the rear axle.

I think this is your best bet.

This is not gonna be cheap.

What's your budget, by the way?

 

[5-7HEAVEN]

You do realize hat installing an engine will make your bunny hops more difficult, lol.

 

[CrimsonPrince]

You do realize hat installing an engine will make your bunny hops more difficult, lol.

You do realize that mounting an engine on the seatpost transmits constant vibrations literally right up your butt!

I'm not sure any person can handle that for long.

What I'd suggest is an engine mounted on the left side rear axle.

There is a kit offered by Staton-inc.com

It uses any engine using a 76mm clutch.
Engines that can be used range from a 1.25hp Subaru to the powerful 4.5hp CY460 engine.

A compact transmission connects to a short chain to a driven sprocket on the rear axle.

I think this is your best bet.

This is not gonna be cheap.

What's your budget, by the way?

I have a pretty liberal budget, but my concern is mounting something thats not "in-line" with the bike, although I dont mind the left side rear axle mount.

 

[CrimsonPrince]

I have a pretty liberal budget, but my concern is mounting something thats not "in-line" with the bike, although I dont mind the left side rear axle mount.

I've seen several BMX rear mount builds using China girl kits with a left side rear wheel sprocket.

Some BMX frames will allow you to squeeze a China girl into them but most of them will require the frame be modified by redesigning, cutting, fitting and welding.

View attachment 105675 View attachment 105676

So basically what im looking at is either a seatpost mount or the rear axle mount on Staton...

 

[CrimsonPrince]

After looking at the rear axle mount, It seems I would have to bore in extra holes into the frame, no?

 

[CrimsonPrince]

You do realize that mounting an engine on the seatpost transmits constant vibrations literally right up your butt!

I'm not sure any person can handle that for long.

What I'd suggest is an engine mounted on the left side rear axle.

There is a kit offered by Staton-inc.com

It uses any engine using a 76mm clutch.
Engines that can be used range from a 1.25hp Subaru to the powerful 4.5hp CY460 engine.

A compact transmission connects to a short chain to a driven sprocket on the rear axle.

I think this is your best bet.

This is not gonna be cheap.

What's your budget, by the way?

So after looking at the seatpost mounted variant, I have a couple of questions as to where I could potentially find the mounting hardware (I circled them in red):

I found a kit on gasbikes.com that would seem to have everything needed EXCEPT for that niche mounting hardware that this guy in the picture is using.

 

[5-7HEAVEN]

If you wanted an inline engine, you'd have to create your own.

Many years ago, there was a rear chain drive kit that lined up the rear engine perfectly with the bike’s center line.

Basically, it was a Titan engine and jack shaft mounted on a flat plate, chained to a left-side axle sprocket.

Using a jackshaft allows you to mount the engine perfectly centered on your bike while having spot on chain-sprockets alignment.

Using a 5:1 pocket bike trans allows you to lower your gear ratio to 15.12:1.