thinking about a motorized bike for pedal assist

nashopolis · #1 (**permalink**) 12-16-2008, 06:13 PM

Hello to all

I am new to the motorized biking world. I have a few scooters, motorcycles, sidecar... all in the name of not taking the car as much as possible. Lately I don't ride that often because of the hassle of gearing up properly only to take short trips. And I need to start exercising more anyway.

So I am really excited about the idea of a motor assisted bicycle.

From what I read so far I am realizing many/most of you all are after a bike that can cruise pretty fast without pedaling at all or very little. Which is totally cool.

I have a different goal and wanted to see if it lines up with reality or not.

My Goal is to set up a utility bike that I can pedal alot of the time but have the ability to kick in a motor for when I don't feel like pedaling or need some help up hills or to offset whatever heavy crap i am toting around.

I want to turn getting to work into some exercise, but still retain utility of motorized transportation to allow me to arrive non sweaty or carry bigger loads without it killing me when I just need to get somewhere.

I think it'll help me get out on the bike a lot more having that freedom or not having to struggle back home when I am tired.

I don't need to go too fast (under 25mph) nor terribly far (probably 10-15 miles max) most days. But I will need torque to get up hills with a load.

Probably Electric hubs, motors make a lot of sense for the task, but I am trying to do this on the cheap and little 2 strokes or 4's simply are way cheaper to set up. I don't want to sink a grand into this experiment right now.

My main question. Since I want to pedal most of the time or assist the motor is a gasser right for me?

a few of my questions to answer to help me decide whether to go gas or electric.

Can you get good torque at low speeds with these little engines?
Can you Start and stop them on the fly easily?
Can you Modulate the power well enough to be able to continue to pedal or does the pull of the engine get away from you almost immediately?

which 2 stroke kits have manual clutches vs I guess centrifugal clutches?
I suppose the centrifugal clutches will require a pull start...is that right?

Does the bike still roll as well with an engine on it (obviously it will be heavier)?

lots of to wade through
thanks for all of your help in advance

jasonh · #2 (**permalink**) 12-16-2008, 06:20 PM

The in-frame 2 strokes add quite a bit of resistance when only pedaling. I would suggest a small (25-35cc) friction drive kit. You would be able to raise the motor from the tire at will so there would be no extra drag. I don't think there is much a reason to go with one of the popular China kits if you only want part time assist.

If you're good at building things, check out the DIY section, lots of people are using small weed whacker motors to build friction drive bikes.

Welcome to the forum.

TexasDav · #3 (**permalink**) 12-16-2008, 10:58 PM

Welcome to the forum. I agree with jasonh, a friction drive sounds like your best bet if you like pedaling and used the motor only when you need the extra power, but It will be hard to want to pedal when you got the option of a motor. Lots of friction drives to choose from. Have fun.

tyrslider · #4 (**permalink**) 12-17-2008, 02:53 AM

Welcome. I have a different opinion to offer, though the others are entirely fine suggestions. I prefer 1 speeds and live in a hilly area; idea is that I help it up the hills to remain up toward top speed and it keeps me movin on the flats. I gear the pedal gear kinda tall like 44/16 or 44/18, I'm most helpful to the motor at 10-23ish mph. So I mainly pedal up the hills and get quite a bit of excersize; I burn a few calories on a 22 mile rt commute. The way there is more down hill, and the way home not so much. W/ the 4 strokes you get drive side freewheel, you can w/ 2 strokes too but I guess most are turned off by wide cranks. Anyway just some thoughts.

Technocyclist · #5 (**permalink**) 12-17-2008, 02:54 AM

Welcome to the forum. First of all, you need a good sturdy steel frame where you can fit an engine. The size of the engine depends on how much you weigh and how much you plan to haul, also depends on the terrain you plan to tackle, and the weather in your area. Friction drives does'nt usually work well in wet conditions

With your requirements, it sounds like you want a very versatile motorized bicycle. And the shifter kit from SBP might just do that if you plan to get Happy Time engine, but you need some $$$ for the shifter kit and it's all worth it. Or you can get a 50 tooth sprocket with freewheel so it does not have rolling resistance from the engine. However, you will need a pull start for it and some wide cranks. If you plan to get a rack mount with centrifugal clutch, then always have some spare clutch springs handy. Rack mount is much simpler, but center of gravity is higher, so it might be less stable.

**Bikeguy Joe** · #6 (**permalink**) 12-17-2008, 05:19 AM

I'm joining the friction drive camp on this one. Easy, cheap, adequate.

nashopolis · #7 (**permalink**) 12-17-2008, 07:26 AM

thanks to all for the replies and ideas.

just a few questions from my research tonight
have folks had good luck with the sickbikeparts front free wheel ? Has it proven to be durable.

where does the rolling resistance come from on the inframe two strokes?

also where I look for a double rear freewheel?

thanks again

B

old motorbike · #8 (**permalink**) 12-17-2008, 07:47 AM

I have a slight drag from the chain and clutch mechanism. I use the SBP shift kit. Their parts are the greatest. Also I rarely pedal.

jasonh · #9 (**permalink**) 12-17-2008, 08:07 AM

On the China 2-strokes in stock configuration, the extra resistance comes from having a chain and sprocket on the left side. When you're pedaling, you're driving that sprocket and chain which is connected to the motor. Even with the clutch in, there is still a bit of resistance. I personally don't like to pedal my bike if I don't have to....it's much harder.