Potential (fast) Road Bike build

[bubruins]

Hello all,

As an avid cyclist and an avid gearhead it was only a matter of time until I tried to fit an engine to a bike frame, especially when engine kits are as inexpensive as they are now.

I had a friend call up and say that he wanted to sell his used 49cc eBay engine kit with all parts (I've actually ridden this setup on a $80 mountain bike host). The awesome thing is he only wants $40 for everything.

Another friend called up within the same week and he has a $80 Raleigh road bike for sale that has 700c's, good cranks, gear system, and good brakes, and some really neat little vintage parts. I'm thinking put one and two together here.

As any other addicted gearhead would do - I've already told both that I'm going to be buying their parts as soon as I can meet them. What I have to do now is figure out if I can make these two work or if I'll need to find a different host.

In total here are the parts I'm thinking about using:
Raleigh road bike frameset (531 steel tubing, 54cm frame)
700c wheelset (mallard hubs, no name rims)
700x23c tires (110-130psi)
6 speed rear cassette, 42/52 chainrings
downtube friction shifters
straight bar
cross levers (pretty effective stopping my friends fixed gear w/ standard road bike brake caliper)

There is a decent chance that I'd swap in my 4340 Schwinn World Sport frame instead and make the 531 Renyolds frame my new fixed gear. It's getting harder and harder to outrun my hipster "fixie" friends while in full fixed gear urban assault mode (soon to be brakeless, too).

I've searched Google and this forum and have found very little about putting an engine on road bike host. One post said that he had to space the rear of the frame to fit the sprocket. Other than that I have not seen much (other than obviously fitting new bars that will accept a twist throttle).

I'd consider myself to be pretty fit as I like to do 20-30 mile rides on my Peugeot at a 14-16mph pace in hilly Nashville, TN. The motor/bike combo would be a kicks and giggles thing more than anything. I know it won't be greenway legal, but I imagine that if I adjusted the gearing 40mph on flats could be attainable with engine power and my own physical input (this would require the pretty 68 tooth chainring that has been hiding behind the glass at my LBS as well as a different sprocket for the engine to wheel transition). Any advice about doing a build like this would be very useful.

 

[biknut]

First of all welcome the the forum from Dallas.

My advise is hurry up and get started. Post a lot of pictures, and ask the forum brain trust questions you might have as they come up. And don't forget the pictures.

 

[professor]

I think there are practical reasons why you don't see road bikes with motors very often.

One is the skinny tires and light rims do badly on potholes.

No suspension. The faster you go- the worse the ride gets.

Iffy brakes.

If you plan to go 40 mph - you need real good brakes. Car drivers are not aware of bikes going fast. They will pull out in front of you or a signal light changes in your path and you will slam into someone if you can't stop fast.

I swithched over to a mountain bike after diving off the road to avoid danger on my road bike. You want every possible advantage riding a powered bike.

 

[placidscene]

I noticed this is a year old thread. I am about to build a motorized road bike with an old Vista 27" road bike and a 66 cc Grubee motor.
I was also looking for some pics or advice on a road bike conversion.

In response to Professor, Dont hit potholes...haha. I hopped a 2x4 at 30mph last week on my road bike that was perpendicular to the shoulder and I had no way to go around it.

I take my road bike up to 40 mph on a regular basis with no problems down hills. I find it quite smooth. Just need good tires. (NOT WALMART!)

As far as cars pullin out in front of you. YES! that happens to me all the time. 2 times in 2 days this week where I had to slam the brakes on my roadie. Thats not cool on skinnies!

I was wondering more about the gearing being powerful enough for the larger wheels. Larger wheels=higher speed at lower rpm, but requires more power to get up to that higher speed.

Has anyone completed a motorized road bike yet?

 

[Sidewinder Jerry]

I use a crank kit on my Land Rider auto shift bike. I've got three drives to select from on the crank and the rear seven shift automatically. My bike weighs 86 lbs and I weigh 230 lbs. I've been able to go up any hill at least 8 mph. I can do 30 mph on flat ground. And have been up to 45 mph downhill. By the way I use a 33 cc 4 stroke engine.

 

[placidscene]

That sounds like more money than I can spend, bit is that 8mph without peddling? Cause I can do that with no motor, an I've had my roadie up to 51 mph down hill.

 

[16v4nrbrgr]

I'm thinking about building up my recently purchased flip flop hubbed fixie into a MB, but I dunno, when I add it all up I can buy a street bike and have proper hardware for running (and more importantly, turning and stopping) at high speed. I'm gonna have to total it all up and see what the comparitive costs will be in the long term. You don't need insurance for a motorized bicyle because it's a moped, but I might need health insurance if I build something faster than it's own good.