Motorbicycle commuter

Hello. I'm Nate.

Right now I have a motorbycicle that I built with the goal of avoiding the legalities, taxes, and hassles of having to deal with automobile ownership. It's not so much that I can 'avoid' it... I still want to drive a car occasionally. But I can deal with the state on my own terms instead of theirs. No drunk driving, speeding tickets, or anything like that. I've basically had a perfect record for the past 10 years (and only relatively minor infractions before that). But it's still irritating. Government mostly blows. The 50cc moped laws offer me a escape... for a while at least.

Besides a virtual small fleet of automobiles over the years I've owned a couple mopeds and a motorcycle. The mopeds are the most relevant to this forum.. a Honda Hobbit with a CVT and a 2-Speed 1970's Puch. Both are fantastic, but the Puch is the fastest by far and I still own it.

The 2-speed transmission on the Puch already means that it's faster then other mopeds you can get. A 80cc(-ish) piston/cylinder kit, performance carb, and expansion chamber means that I can reach speeds up to 50 mph. (clocked by my brother following on my motorcycle). But the thing is beat to **** and is in serious need of a entire-bike rebuild. Bad forks, bad springs, back breaking shocks, leaking carb, gas tank that regularly gets water in it, electrical system put together by goblins (not my fault!), rear wheel held on not by 2 nuts, but by a nut and a hose clamp, no rear brake, bad front brake, etc etc. It's a exhilarating death trap.

Plus I've moved to a new state in search of gainful employment and all my toys are left behind in my house with a friend renting it. So now I am challenged by Georgian traffic (Atlanta area), rising gas prices, and a 20 mile commute.

The obvious solution is some sort of scooter. A scooter is far more useful vehicle then a motorcycle. Cheaper to buy, more efficient, more reliable (typically). It's easier to ride, easier to carry stuff in, etc etc. The Chinese scooters lack performance, but make up for it in price. I can get a 800 dollar 150 or a 600 dollar 50cc locally. 150cc and 50cc scooters are some of the most common vehicles in the world and can be made to be dead-on reliable as long as your capable of preventative maintenance. Japanese/Korean scooters are easily 2-4x more expensive, but can be reliably driven and maintained by a eggplant... not to mention are quite a bit faster.

I almost had 150cc Chinese scooter. Practically had money in hand, but i decided to hold off a bit. After looking up motorcycle licensing requirements, insurance costs, registration costs, taxes, etc etc. I decided 150 was too much hassle compared to a 50cc.

However 50cc is going to be slow and is not going to be able to keep up with traffic.....

After thinking about it for a bit I decided that if I am going to buy a slow vehicle like that then I'd get one that would be recognizable as being slow and be easily acceptable by the general public without a second glance... not to mention the ability to pedal in case of failure or used up gas... AND health. I LIKE pedaling and having the ability to move around on my own power. Since I stopped smoking pot decades ago in high school and no longer have any desire to drink alcohol (dreadful stuff, except the occasional 2-3 beers) the best way to get high for me is to pedal my fat butt up a 3/4 of a mile hill as fast as I can. Fantastic stuff!

Hence a bicycle. but with a 20 mile commute....

Hence a motorized bicycle.

I love it.

My 'NaterBuilt' Motorbicycle revision 1.3:

This is how my first creation turned out. It's built using a Trek steel-framed 820 bicycle with a GT4 Grubee 66cc motor kit bought from Pirate Cycles. Shopping with Pirate Cycles was a good experience and the 150 dollar kit is a fantastic value.

This forum was a invaluable resource and has given me lots of great ideas. Thank God for the internet. It's a fantastic resource and makes all sorts of things previously impossible and expensive, very possible and cheap.

My observations on the GT4 kit:

The engine is fine. It's extremely low-tech, but put together decently. For the price offers a unbeatable value. I don't like the mounts through. Custom frame mounts are a very good upgrade. Unless the mounts match your frame exactly I expect that any long term installation (several years) will result in metal fatigue failures around the mounts if you keep them 'stock'.

The carburetor is fine. It doesn't leak and it does it's job reliably. Suppose to be a upgrade compared to the normal fair that you get.

The 'rag' type rear sprocket is irritating to put on, but it works great. I have no problems with using a rag-mount type rear sprocket!

The controls are 'ok'.

I don't care for the throttle controls. It's very cheap and a bit complicated for what is needed. But they work just fine. So it's ok. A metal replacement from NAPA auto stores would be on my Todo list.

The clutch control is fine. Just a generic child bicycle style brake lever. Works as advertised but people with weaker hands will have problems with it. The lever probably should be longer for more leverage.

The chain is cheap. It stretches way to much when it warms up and shrinks back down bizarrely. I don't understand it, but makes it nearly impossible to get the right tension without using a spring-mounted idler wheel. A new chain from Tractor Supply of the same size would probably be a good idea for people wanting a lot of use. But it's strong and big enough that it will work out as advertised. It was not damaged, rusted, or stiff when I got it... unlike other people's experiences with other kits. I was fine enough with it that I used it. It's just not optimal.

The gas tank was fine. It has a cheap cap that is crying out for a upgrade. It was dirty inside also. Not full of crap, but it's not something that can be eat off of and surface corrosion will cause problems with the carb. But I ruined the tank trying to screw in the cut off valve. MY FAULT. I don't blame the kit for that.

YOU NEED A SEPARATE FUEL FILTER. You WILL run into issues with the carb without it.

The 'tensioner' is a piece of crap. Very easily the worst designed and most dangerous part of the kit. It is abhorrent in all forms and there is not a single positive thing to talk about it. The world is simply worse off as a whole that this crud even continues to exist. It makes babies cry.

Basically this is what will get a HUGE number of people into trouble:

* You buy the kit and put it on.

* The last bit you will probably mess with before driving for the first time is fiddling with the chain tension. You know if it's too tight it will cause problems, and too lose it will flop around and probably do something bad.

So you get it on so it's 'ok' tight.

* You get on your bike and ride around a bit. You get back and notice that the chain is flopping around a tiny bit. So you sigh and work on the tension a bit more.
* Eventually you get brave enough that you take it out for a long distance ride. Plus you go fast. Things seem to go well.
* When you get back you notice your chain is flopping all over the place. It's VERY loose. So you swear a bit and fix it before going inside....
* A couple days later you get back on your bike and take it for a spin. A few blocks later the stupid real-wheel chain thing EXPLODES on you. The chain will break shredding something. Or pull the tensioner down into your spokes and ruin your rear wheel while causing you and your bike to crash hard. Something really bad.

What happens is that you put the tensioner on and tighten it down while the chain is still warm and lose. When the chain cools and sits for a while it tightens back up and will create a HUGE amount of pressure. When you combine that with a 2-3 HP motor it WILL do something very bad. Something WILL break.

So the only right way to run this kit stock is with a floppy chain. Upgrading the tensioner is a MUST. It won't stay tight, it won't do it's job, it will eventually rotate down into your spokes. The bolts are cheap crap, the plastic wheel is not only weak and won't line up right, it's brittle. The thing will sit at the wrong angle always since it's clamped to the chain stay that probably is not parallel with your chain. The bearing surface will probably fail and the wheel will stop turning and your chain will be forced to slide across it. For as long as you use it you will need to keep a eye on it and do a inspection EVERY time you ride your bike.


The final big part of the bike is the exhaust manifold/muffler. I hate it. It's just not designed well. It's restrictive, it doesn't do a good job of muffling, and I lost the bolt and the bottom cap of the muffler the first time I drove it any distance. This is even after I inspected it and tightened down the bolt since it had started to come lose. Supreme irritation.

A proper expansion chamber would be a MASSIVE upgrade that nobody will regret as long as it fits on your bike. Not only increase power and fuel economy, but just sounds and looks better.


All in all it's a good kit. It's a great starting point for a a great bike. The 66cc motor has a lot of potential and it should be reliable enough and parts are cheap.A very suitable toy.

Here is a picture of my bike before the reconfigure:



Here is a video tour:
YouTube - Motorized bicycle commuter version 1.3


Significant differences from the kit are:

* Custom PVC gas tank
* Silicon Tubing Exhaust with lawnmower muffler and 'Red bull' extension. The extension contains a copper tube with numerous holes drilled into it and is packed with fiberglass.
* Custom 12 volt LED headlight and taillight system.
It consists of a:
MR16 style LED light in homemade housing.
LED taillight intended for trailers on rear.
12v 9Ah AGM Lead Acid battery
Automotive style cigerette lighter for phone charger and other accessories. (will also allow for charger)
"Medium Duty" 2-post switch with dust cover
* Blue plastic toolbox mounted to front of frame for housing tools and battery electrical system.
* Aluminum rear rack
* Expanding Bell basket for carrying things.
* A fisherman's accessory bag from walmart (had two velco loops that allowed for attaching to bars)


Since then I've put a different motor on it....