Bike ? and 4-stroke ?

[underaged!]

Some of you may have read of my Weedwacker/bike. My Daddies lawn mower recently died, so I inherited it. The motor runs fairly well, especially for it's age. So anyway, I'm planning on rebuilding my bike with that motor.

I'm looking for low-end power, to beable to climb the hill up to my friend's house near the school. Is a long wheel base bad for this? Does adding "rake" (correct term?) or bending the forks/ angle the neck part to angle the fork, handle bars etc. seriously adversely affect handling?

So if I ever manage to chop and strech the frame to get the motor mounted, I heard that if I want to be climbing, then you have to try to have the least amount of weight on the rear (propelled wheel). Is this true?

Can I convert from an old fashioned style float carb to a diaphram carb? Is it ok to use the idler pulley (correct term?) system that was on the lawn mower, to transmit power to the wheel?

Any answers, tips, or advice would be appreciated, thanks.

 

[mwerner]

Without adressing too many of your questions, a few things:

You see rigs like this every once in a while; you might want to check with your local laws to make sure you'e not building a "motor vehicle" that would require licencing and such. Most states allow motorized bicycles or mopeds, but have limits on engine size.

Stretching the frame to accomodate the engine shouldnt' be too hard, but bear in mind that bike tubing is very thin, you have to be careful while welding.

Altering the head angle/rake will affect handling, but this seems to be a very common modification on both bikes and motorcycles, so folks learn to cope. Mostly, low-speed handling suffers. Make sure any extended forks are plenty strong to bear the increased strain and added weight.

Do you plan to retain the ability to pedal? If so, the drivetrain will require some thinking. I was looking at a commercial rig at one of the local bike shops with a two-stroke engine neatly mounted in the frame. Centrifigal clutch, and power to the left side of the crank through a kind of freewheel system. You could still pedal.

Also give some thought to brakes. With increased weight and speed, stopping ability will be important.

 

[Cougar Allen]

Adding rake makes it want to go in a straight line. That's a good thing if that's what you want to do, not so good if you want to turn.

How steep a hill is it? If you're building a hillclimb bike ... when you're climbing a steep hill/easy cliff all the weight falls on the rear wheel and you want to keep enough weight on the front so you can steer ... otherwise you find yourself on a motorized unicycle.

The easy way to motorize a bicycle is to mount a little motor on the front fender to drive the front wheel. Your motor might be too big for that though.

 

[underaged!]

I'm not planning on pedaling. The hills not that bad, I'll try to get some pics later. The tubing on the frame is pretty thick, I think the bike is about as old as I am.

And ya, the motor is way too big to put on the front. I think I'm just going to go for it on monday. God help me.

 

[mwerner]

Honda makes a cute little rig that mounts over the rear wheel, and transfers power by friction.

Likewise with a little French two-stroke that mounted on the handlebars on a pivot, and drove the front wheel with a ceramic roller. Thing actually had a lever that you could use to push harder if the the street was wet! I don't know if they still make em'.

 

[underaged!]

I'd like to do it myself, I have the equipment and I think I have the skills. I've done it 3 times before, but 2 times were spindle/friction drive as mwerner described(same as how Go-peds are driven) and one was chain w/cluch. So this is a little different. Also this time I want to climb all other things were fine on flats, but hills were the devil. Oh, and this is going to be the biggest (displacement and size, not HP) motor so far I'm doing this stuff with.

 

[underaged!]

Ok, I got some pics today walking up to school. I could of got a nice picture over looking pearl harbor and central oahu. Too shame though, sometimes tourists come around the school and do that.

These two are around the same place.


This looks to be the biggest/steepest hill, it isn't bad, but IDK if I can build the bike to get up it.

Same one but on the top, looking down.

 

[underaged!]

Ok, so I think I know how I'm going to chop the frame.

Should I not be cutting the section the seat post goes into? I'll try to brace it up after I get the motor and idler pulley in...

Is there any cheap and easy way to lift the bike? Otherwise adding rake would be out of the question. I'll only have about 3-4 in. of ground clearance when I chop and put back the frame.

The chopping starts tomorrow.