Is it possible to Motorize a bike with coaster brake?

GoldenMotor.com

T Rock

New Member
May 5, 2010
38
0
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Florida
I have a huffy that im trying to install an engine on and im having a problem with the rear gear and the coaster brake. I bent the coaster brake to clear the heads of the bolts for the rear gear and now the rear wheel does not spin freely, whats the deal? Having a real hard time trying to get the rear wheel adjusted properly. Any help would greatly appreciated...Thanks...Tom
 

psprat496

New Member
Nov 22, 2009
159
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New Jersey
I have a huffy that im trying to install an engine on and im having a problem with the rear gear and the coaster brake. I bent the coaster brake to clear the heads of the bolts for the rear gear and now the rear wheel does not spin freely, whats the deal? Having a real hard time trying to get the rear wheel adjusted properly. Any help would greatly appreciated...Thanks...Tom
IMO scrap the whole coaster brake and get yourself some V-Brakes at least. I think it's a must with these motorized bikes. The coaster just isn't as practical.
 

T Rock

New Member
May 5, 2010
38
0
0
Florida
After reading your blog about trimming the dust cap, I think that is my problem. I will give it a try before going to a hand brake set-up. I will be getting a front and rear hand brake set-up in the future, but just wanted to get this thing running. Thanks Bikeguy Joe
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
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Phoenix,AZ
Coaster bikes make the best MB's in my opinion.
All you have on the handlebars is the throttle, clutch, and front brake.

Put the bolts on the sprocket going through to the inside of the wheel, not sticking out to the outside.
And yes, the dust cover can be an issue.
 

silverbear

The Boy Who Never Grew Up
Jul 9, 2009
8,325
670
113
northeastern Minnesota
Coaster brakes on vintage bikes seem pretty good in my opinion. I don't know about the new ones. A brake up front is essential even if you ride at very moderate speeds. If the chain derails or breaks, there's nothing to stop you. A caliper brake up front is OK, drum it better, disc (I'm told) is best. I'd keep the coaster brake and add the caliper brakes you have ordered. Unless you're screaming around trying to set land speed records it should be plenty good. The faster you go then the faster you need to be able to stop.
SB
 

bairdco

a guy who makes cool bikes
Aug 18, 2009
6,537
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living the dream in southern california
i love coaster brakes, because i've used them forever and know how to maintain them, and i know how they work, inside and out.

the newer one's are pretty cheap, and taking them apart for re-greasing scares a lot of people away, but it comes down to preference.

my bikes have all been vintage builds so far, and the coaster is the way to go to keep the look and style i want.

also, if you search the coaster brake you have, you can probably find a site that shows you how to rebuild it.

as far as it not fitting right with your engine, that's a common problem and an easy fix. the dust cap is the biggest hassle with them, but after you fix that, hopefully you'll have no more worries.
 

Whizzerd

Member
Nov 20, 2009
114
21
18
Muncie,IN
It may not look real cool, but I've gone to a mtb shock fork w/ v-brakes on the front and coaster on the rear. Personally, I think properly adjusted v's work better than the drum. Probably the best and most costly would be disc front and rear. If I had a shift kit and traveled 40+ mph you betcha there'd be discs on the bike.
 

Easy Rider

Santa Cruz Scooter Works
Jan 15, 2008
2,145
7
38
Nor*Cal
Yes its possible but there is a down fall to having one. My first bike had a coaster brake and I loved it for cruising but if you ride fast (in the 30's)...beware. A bunch of us were racing down a street and had to brake quickly. Well to make a long story short, my lever clamp snapped and jacked up my frame when it spun around. Also, coaster brakes aren't good for windy roads or quick stops. Ask Dean, I slammed into him a few times. lol
 

T Rock

New Member
May 5, 2010
38
0
0
Florida
I trimmed the dust cap and now it works great, the wheel spins freely and no binding, Thanks for the help guys. I found out that basically the dust cap must fit through the center of the rear sproket, if it dose not well then it aint going to happen and binding will occur.
 

KCvale

Well-Known Member
Feb 28, 2010
3,966
57
48
Phoenix,AZ
I read a very informative and detailed web page about coaster brakes.
Overhauling a Coaster Brake Bike

I have noticed that newer Beach Cruiser coaster bikes seem to have a weak coaster brake, so I went looking for why and how to fix it.

Turns out it is a matter of gear ratio, not the brake itself.

Coaster bikes tend to be geared a little high so you can get up to a fair speed without gears.
But this means it takes more effort to get them started.
The reverse is also true, it takes more effort to apply sufficient braking force.

The simple solution for a better coaster brake seems as easy as just lowering the gear ratio a bit by swapping in a rear sprocket with one or two more teeth.
It's a fairly easy job, and the sprockets are only about $15.

Since the vast majority of the pedaling you do is low speed, it would seem to be a win win, especially on the those days when the motor is stubborn to start and you have to keep pedaling to turn over the motor.

I am aware the pedal chain will need to be longer, that is not an issue for me, I already size the pedal chain to match the drive chain so I don't need to use any tensioner.

Has anyone already done this?
If so, how many more teeth? One, two, maybe even 3?
I suppose it would depend on the current gear ratio, but a little trial and error won't hurt ;-}
 

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
7,266
1,797
113
Los Angeles, CA.
The gear ratio of the sprockets has nothing to do with the problems of modern coaster brakes... The problem is that they can over heat & lock up.

I totally agree with Baird, older coasters seem to work much better than modern ones.
 

Alajoyn

New Member
Sep 28, 2009
71
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Portage, MI
The gear ratio of the sprockets has nothing to do with the problems of modern coaster brakes... The problem is that they can over heat & lock up.

I totally agree with Baird, older coasters seem to work much better than modern ones.
Great response on this issue!
On my tandem (85lbs w/o riders)(390lbs w/me & wife) I reverted back to the original HD coaster brake and a front and rear caliper. I can hammer down safely using all 3 from a nominal speed of around 22-24mph nicely and not over use any one system. I did R/R the coaster with cleaning and new grease before reinstalling it. The cost of converting to disks wasn't worth it to me.

These guys are giving you great advise.

Robert
 

bairdco

a guy who makes cool bikes
Aug 18, 2009
6,537
264
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living the dream in southern california
kc vale, you're right. i've had this argument with people before about gear ratios and coaster brakes. the smaller the ratio, the better the brake works.

i had an old bike with a 52tooth front sprocket, and switched it down to a 36, without doing anything else to the bike and the brake went from barely stopping to locking up effortlessly.

it seems odd, because you figure all you need to do is pedal backward and it should stop, so gear ratio shouldn't really affect it, but it does.

i still don't know why exactly, but i know that it's true.

also, it's very true about older coaster brake hubs working better and lasting longer than new hubs. as long as they're not worn out from age and use. compare an old bendix 76 to a KT or hi-stop, and there's a world of difference.

there's a new hub called a "velosteel" which is based on the 50's Sach's Komet hub that's supposed to be the best around right now. i'm gonna lace one of those up soon and try it out.
 
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happycheapskate

New Member
Nov 26, 2009
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Rockwall TX
I like coaster brakes on motor bicycles. Mine is working quite well. I have a front caliper brake too.

I removed the dust cap, and installed the cog over the hub there, backing up against the spokes. The cog is held in place by the given bolts and nuts and one rubber washer and moon clip set, just eliminating one of the washers of the conventional setup.

The dust cap was flattened to fit back into place under the coaster brake arm, against the cog with a little grease under there.

I've been using it half a year. PS its a Hi Stop and it works fine.



HOw the coaster brake increases power with lower gears:

The use of a bigger rear cog (pedal side), or smaller front cog, gives the crankarm larger leverage over the internals of the hub which push out the brake shoes into the hub to brake.

It is a similar effect as you would have by using a longer crank arm.

If you can find 180mm 1 piece cranks (BMX shops), they will not be as comfortable to most riders, but would give much more pedaling and breaking leverage.
 
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