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Old 05-27-2008, 05:49 PM   #1 (permalink)
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DIY: Honda c70 Passport Electric Conversion

Hello all, I am in desperate need of some serious guidance.

I have recently bought a 1982 Honda c70 Passport for 175$. It is in need of serious repairs and after consulting several people and looking at the machine on my porch, I'm beginning to think this may be more of a project than it's worth. So I'm thinking about converting it to an electric moped instead.

What I need is a vehicle with a 15-20 mile minimum range (I have a 5 mile commute to work and need to be able to get to and from work with some extra margin for error)

Ideally it would have a top speed of 40-50mph (the highest speed limit on my way to work is 45mph, I would like to still get to work in a normal amount of time).

And now here's the big one, I'd like to do this for under 500$ (not including the 200 I've already spent)

The information I really really need is what to look for in a motor (even specific motors to look into). What kind of batteries to get (amps/volts etc. etc. as well as specific examples).

One idea I had for adding distance to this vehicle was adding pedals to add exercise and charging (the problems I can think of with this idea is that the bike is almost 200lbs and so pedaling without the motor on would be useless without a very specific gear ratio, and also the pedals would be hard to place).

So take a look and let me knwo what you think I'd really appreciate any and all help.

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Old 05-27-2008, 10:38 PM   #2 (permalink)
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Hopefully Ben will chime in here with his electric motorcycle building prowess, but this is definitely a project I'd like to see happen.
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Old 05-28-2008, 09:12 AM   #3 (permalink)
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how good are you a finding really good deals? like motors for almost free, controllers that someone left to you in their will, batteries that you stole...
If I was building this out of that bike I would put the batteries in a trailer to give better balance, control and more space for batteries, but because parts for those are really cheap I would say rebuild it and have a 150mpg motorbike, what all does it need? they are solid little engines.
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Old 05-28-2008, 10:44 AM   #4 (permalink)
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I'd think you would be able to get 3 car size batteries on that bike, one between your legs and two behind you on a rack, and maybe another where the motor and tranny was.
I had an 81 CT110 when I was 14, wish I still had it... It would only do about 53mph but that's with knobby tires and maybe a higher gear ratio, it basically ran out of revs if I can recall. I would hardly notice a 5 gallon gas tank on the back rack so I think you would be good with batteries there.
I wouldn't take it on the highway though, for short sections sure but not for miles, some stressed out person in a "cage"(car) will tire of your 47mph into a headwind and do something dumb. If you can find a quieter/slower route to work then it would be ideal.

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Old 05-31-2008, 01:32 PM   #5 (permalink)
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Well as for fixing it up... I've had a few mechanics look at it and although it's doable... the consensus is that it's not really worth it... big ol crack in the left crank case? cover (that or engine cover or something) plus a myriad of missing parts (mostly electrical/aesthetic). I bought the bike for 200$ and it looks like close to a 1k to fix (over 300$ in parts). I've done the research and a new bike would still run me as much, but the problem is that it's outside of my budget for a high gas mileage vehicle (under 500$). I really like this bike... and because of it's condition I really don't think I'm gonna get my money back trying to re-sell it.

If I were still back home (California) where I have friends who do this kind of work and could get the labor cheap/free I could afford it, but even an at-home mechanic charging 20$ an hour it's still too much. I'm not sure what is more of a pain about this, that I bought it and I don't know if I can ever ride it, or that after doing a lot of looking around I can't think of anything else I'd like to get (mopeds don't really fit the look I want and motorcycles aren't the MPG I want and I'm still wary of riding something over 150cc right now)

Anyhow back to this project, assuming I did convert it I would probably pull out the gas tank (under seat) and try to cram one or 2 batteries in there, put another on the back rack and possibly a 4th above the engine (mounted to the beam), I would probably have to change the sprocket ratio's(?) in order to get the kind of torque I would need to carry my frame (210lbs) up the final hill to my apartment (fairly steep and long), and I would definitely need a powerful enough motor to do it.

Another thought I had was possibly changing the vehicle to a bio-diesel bike. Although the electric conversion has a certain romance to it that I like, I think it might impractical due to the hilly nature of Ann Arbor Mi (where I live) not to mention the fact that there are no outlets near where I can park it... and it's a bit heavy to pull up the short 6 foot flight of stairs to the back porch EVERY night. By putting a whole new diesel setup on the bike it would probably mean a whole new engine right? I realize no matter what I do (Fix, electric conversion, or diesel conversion) it is going to cost way more than I want to spend, but if it works (especially the bio-diesel/electric ideas) it would pay for itself in only a few years, plus it would be fun!

I really know nothing about this kind of work so I really need lots and lots of ideas and brainstorming on how to go about doing all of this. I think I will create 2 separate posts for this project, one for the electric conversion, and one for the diesel... if you have ANY ideas on where to start, etc. etc. please let me know.


p.s. I will edit this post with pictures and links to the other post in a bit

Here's the link to the Diesel Conversion Post (complete with poll asking what you think I should do with the thing)


Last edited by papaslides; 05-31-2008 at 01:58 PM..
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Old 05-31-2008, 10:28 PM   #6 (permalink)
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Hey Sean,

After reading through everything you posted, I don't think an electric conversion is the best way to go.

The current stats on my cycle at 20 mile range and 45 mph top speed - just as you said you want to go for.

My cycle weighs 400 lbs.

Load weight onto your cycle until it weighs 400 lbs and go coast down a hill. See how it steers and how the suspension bounces. I don't think it will work out too well.

This is a very "scooter-esqe" style frame. Cool looking, but where do you put the batteries? My cycle has dual down-pipes, so I have room for the batteries to mount on.

I would echo comments about repairing/replacing the engine. Gasoline or diesel pack a lot of power in a small size. For a lot less weight and space than batteries.

I think my batteries hold the equivelant of about a pint or less of gasoline!!!

Yours is a cool little cycle, but I don't think it has the space or suspension for an electric setup.

Explore other possibilities of what you can do with this cycle. It could be a really cool little project.

I like the idea of a 150 cc engine with an aerodynamic fairing on it.

Best of luck,


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Old 06-05-2008, 11:08 PM   #7 (permalink)
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Ooooh Ben, great idea... ok I know I'm kinda spamming the boards this way, but I'm a bit of an organizational ocd case so I really can't start a new idea in this thread, so I'm gonna do what I did with the other one, link to a new thought process... this time, rebuilding the honda c70 with a larger engine and possibly an aerodynamic fairing.

I will post the link in a minute

edit: here's the link

Last edited by papaslides; 06-05-2008 at 11:26 PM..
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Old 10-06-2009, 09:03 PM   #8 (permalink)
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I have some help for your passport. I have a 1982 c70 passport with 433 miles. drive it home when i get the new tires shipped to me. this little baby if nice. redford mi.

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