Monday, November 12, 2007


Mopeds Are Everywhere

Blue: Pedals Required
Green: Pedals Not Required
Yellow: 50cc No Restrictions

Mopeds are far cheaper for young adults to get on than cars. A car requires all this heavy insurance and lots of gasoline and complex engine maintenance. A cheap moped can cost $275. Well, a used 4-stroke will probably run a few hundred more. Some weigh only ~150 pounds, and get "81 km/l". 81 km = 50 miles. 1 liter is 1.1 quarts, so there are 3.63- liters per gallon, giving us 181 mpg.

Some areas do not allow mopeds to travel faster than 25mph. But a moped could probably be coaxed up to a much higher speed. Some also have pedal assists. This site produces stats for Hero mopeds. They appear to be 49cc.

The Jawa 50 Robby is a 4-stroke moped. It goes 28mph with a 0.0419Hp/kg power ratio.
The Honda CD 50 Benly is a 4-stroke moped with a 0.05Hp/kg power ratio. This figure should be high on vehicles. The honda does not list the speed, but simply by having a higher Hp/kg than Robby, it will probably go faster. This Yamaha YB 50 has 0.0471Hp/kg, but its name is annoying. The YB-1 Four is almost as annoying, but has 0.0494Hp/kg, but its compression ratio is lower than the Honda.

This Honda V-2 Magna cruising moped makes 26.82Hp, and weighing 372 pounds has a 0.1559Hp/kg rate. The MPG on this page must be inaccurate. I'm really looking for something with pedals, though.

No obvious pedals here, but the Honda Monkey 50 has the highest smallbike Hp/kg at 0.0534, and it's also a 'naked bike', which means almost nothing to me, except that it's 60 pounds lighter than the others. It's also got a lot of positive remarks. I might swing for a monkey. NAKED!! Someone said $500 euros. Someone else said 450L$, which would be like $700. $895 for this motorcycle-shaped moped.

But enough non-tech talk...

This is how to get your moped to go 90, minus safety precautions.

The following is how to tweak your moped to do 45 or 60 thereabouts:

Sunday, November 11, 2007


Tweeks and Other Advice

Sprockets/gears with different numbers of teeth will produce different performance. Where a normal Tomos Streetmate with a 26 tooth gear will strike 26-28mph, the 24-tooth gear will give it a top speed of 36-38, and the 22-tooth will put it at 38-40. This does not enhance the power of the bike, though, so it necessarily gets to the higher speeds with less acceleration and produces less torque [netwon-meters/NM]. But it will go faster and should perform better downhill.

The chain is another area of concern. Keep it well oiled and if it is rusty scrape it off or replace the link. You'll also want to keep a good amount of tension on the chain. It should be just tight enough. If you change the sprocket gearing you will probably need to take a link or two out, but not too tight or it will experience more friction than optimal. Too loose and it'll sag. Anything that sags on you or your bike is not optimal, unless it's a great pair of breasts, and even they make it hard to run fast or jump high. I am leaving that comment in the final text here. Make sure the links turn well. A sticky chain will rob you of valuable speed.

Most bikes have a bottleneck somewhere. Depending on the bike, yours may benefit from boring out the exhaust pipe to allow greater air flow to the combustion chamber. Fuel mixed with more oxygen burns more quickly and more completely, providing more force and less chalk in your air line. The piston may also be able to reach higher RPMs. You may be able to use a special drill procedure to bore your exhaust pipe wider. Research your make and model before trying this and do it in safe manner. It is possible to bore out a carburater to help it push more air as well. This is a specific kind of custom job and requires mechanical skills and good tools to perform.

carb talk:
"yeah, i upjetted the crap out of it. the stock on a 2hp is 62. I upjetted to a 74. i also moved the needle position down 2 slots to increase gas (like that does much though)."

You might also want to check the ignition timing. If the timing is off or too weak it will reduce power. Your spark plugs should be well timed and strike often and with a high wattage level. You may also want your spark plugs to strike for a longer duration, if this is possible. It could potentially help provide more complete combustion.

You can also have your pistons' holes bored wider and milled down deeper to let them hold more fuel and generate greater compression of the fuel, again producing more complete combustion with more force. Don't bend the metal! Wider holes require wider pistons, so this is a more expensive job. You may also need to adjust the timing for milled holes, but it could be fine. You can also use lighter material pistons, which will spin up faster. Anything that moves could use less inertia on your bike, and the more it moves, the more it could use it. This is pistons, cams, flywheel, wheels for the most part. This is money, though.

"No, no. The speed kit is NOT used for torque. It’s used for hp. Why? A kit makes your bore larger rather than your stroke. Increaseing the bore=hp while increaseing the stroke=torque. Your speed kit though should add around 10 mph while the Bi Turbo is 5."

Your bike probably doesn't have a fan, and may even be air cooled, since those engines are so small, but turning on the heater full blast will wisp heat away from the engine. This may be more valuable of a trick in a car or more enclosed engine, but a cooler engine is actually *smaller* and the pieces are closer together, producing better connections. A cooler engine can operate slightly faster as well. If your bike is air-cooled, it is probably too small to benefit substantially from water cooling unless you've put some interesting tweaks on it already, in which case you're an expert. You could also benefit from putting a supercharger on it instead of a carburater, but this sounds freakishly expensive for a moped or bike, and engines not designed for the increased pressure and power of a supercharger will not respond well to supercharging and reduce the engine's lifespan.

Your engine still requires air, though. Always make sure your air filter is clean, to allow the most air to get through anyway. And if you haven't already checked your spark plug[s] unscrew them and brush them off with a little file if there's any gunk on them. You might want to do the same to the battery every now and then. And change the oil. And brush your teeth.

You may also be able to make your bike lighter by taking non-functioning stuff off. Anything that rattles or shakes is taking power from the engine's forward operation. If you have a car, you could actually raise the roof. I mean, lower the roof, to reduce profile. That is kind of like a lowrider. You'd better be short, though.

Many bikes can make good use of 12 volt lighting systems to shine brighter. Heck, put in a second plug while you're under there. It is always a good idea to add additional reflectors anywhere on the bike and to provide custom stickers and wax graffiti or good decals to the bike. That kind of style will make it go like 10 times faster. No, it won't change a thing.

I am also going to recommend disc brakes if your bike doesn't already have them. You'd be surprised how much better your bike will corner at high speeds if you have good brakes to assist you, and anytime you need to stop, like a dangerous situation, the brakes will not fail you.

You might also want to expand the gas tank, if your tank is small, or if you go trekking often. It's not always enough to just carry around a J-can. Fuel weighs, though. See: Hydrogen.

And make sure your bike's fluid levels are all optimal. You'll want plenty of transmission fluid if it's a multi-speed dealy. If you've got a radiator or liquid cooling, keep that fresh and full. Always change your oil at the recommended time, if not sooner. I've been told synthetic oils can last 5000 miles in an automobile, but once you change it, the thing seems slightly more responsive. That is joy. Engine joy.

I hereby (c) "Engine Joy" as a custom fuel additive. "Engine Joy" will be more viscous than normal fuel, so as to free gunk stuck in the engine. This will make an oil filter change necessary after only a few tankfuls of fuel so as to eliminate the freed gunk. This should increase performance substantially. Engine Joy will also have very high octane rating. Perhaps 115, to increase the fuel's octane rating. A high octane fuel will increase BTU/h produced per pistonful. This will probably not be noticable unless the ratio between Engine Joy and normal fuel is high. It will also contain a fuel stabilizing agent so the gasoline will not break down over time. It might also contain agents that will break down air pollutants after combustion.

It may be worth it to put on a windshield if you don't have one. You can do this with a metal drill bit, some washers and bolts, and a good piece of plexiglass. Keeps the bugs and rocks out of your face [you are wearing a cool helmet, right?] but it will increase your wind profile. Tuck your body down close to the bike to reduce the wind profile as well. =) You might also want to attach saddlebags or add or make other compartments in the vehicle for storing things like tiny dragons or luggage.

Large tires will be a good asset. The tire is like another gear in the setup, with the last gear being the earth itself. If you have a large tire and enough torque it will do the hi-trick nicely. A small tire will provide more torque but lower top speed. Always keep your tires properly inflated. You'll want as little sag as possible in the outer wall. Slick tires without grooves grip the road better for more acceleration, but they will also produce lower top speeds and perform terribly in weather or on loose track. Plus it's just a bike. Replace your tires when you can't lodge small things in the treads anymore. Inflating your tires properly will give you better gas mileage as well. This works in cars also. Most car tires get up to 44 psi, but they only tell you to inflate it to 32 or 34. Driven-on tires are hotter and the psi increases, so I'd say put them up to 38 or 40 and take it from there. 44psi would be too high. Let some air out. 50 would be right off.

You can also get narrower tires. Every place where the tire touches the ground is drag. A lower profile tire will produce lower drag and higher top speed, but may sacrifice acceleration and grip, which can affect cornering, handling, and braking.

If you get the chance, get some extremely sweet/smooth shocks. Having better shocks will actually increase the performance of your bike because you can go faster over rough terrain, your engine will be buffeted less [as will you], and you will have better control of the vehicle. While you're here, you may want to get a better seat for that thing. I know bikes sometimes have uncomfortable seats. Take it from Lance Armstrong. Use one of those seats with the dip for your stick. You could probably tape some of that egg-crate foam over the seat. Oh, man... egg crate foam... so foamy... you will like that modification.

And while we're here it is always worthwhile to put leopard print on your moped. It's already so triggy that leopard print is the only way to go. I've seen it done. It looks good.

Never revv your engine in neutral. It may sound loud and have no load attached, but it is one of the worst things you can do for it. In the same way, do not dry-fire slingshots or revolvers and do not throw a knife down on rock. You'll warp it, bend it, or mess it up. Tell this to people who do it to their expensive cars. Don't do it to your cheap bike, if it has a transmission you can modify. Also, know that revving your bike's engine very high all the time is not how it was designed to be ideally used. Going full throttle will also pull on the bike's internal parts with high tension. The bike will respond, but doing this will shorten the engine's lifespan. You also get non-optimal mpg when you accelerate quickly or ride in the red zone.

Using a higher octane gasoline may increase the BTU/h produced from your fuel. A 4-stroke engine should be using petrol. Those 2-stroke things pollute a lot and use oil/gas mixture, which is another hassle. If you usually burn 87-octane, try the 93. The benefit will be greatest if your engine is tuned for higher force and if the compression ratio is higher, but you may experience some benefit just by using the better fuel. The change may not be worth the up-power in mpg vs cost.

"OK… I have a tomos lx 2003 and i have a crap load of stuff on it….shaved manifold, 70cc, biturbo, carb, intake, airfilter, sproket, and I have done a little tweaking. My moped can hit 50 and hit the pin with a slight incline. Now i was talkin to this kid from moped army and he was sayin he weighs 150, 20lbs less than me only has the biturbo and 70cc and he has hit 70mph. When I heard this I said wtf a tomos cant handle that speed yet he swears by it. Now is it just me or is this a bunch of BS. RESPOND WITH WHAT YOU GOT AND WHAT UR TOP SPEED ON FLAT IS!!!!" -technically not a moped. This would qualify as a light motorcycle. For the money you might as well! A moped can probably be tricked out to hit 65mph or even higher, but the bike and these modifications will probably cost you getting on to $2000. That is rounding motorcycle territory. Plus going that fast on such a tiny bike can be downright not safe. Plus the original parts are not tuned to be optimal at such high speeds. You'll experience a lot of redline-oriented parts drag at those speeds, and have to overcome numerous bottlenecks to get there. You might want to switch to a Honda Rebel or something if you get super serious with the moped.

The law says that you are not to drive a moped over 25mph, so this is for non-state road use 'only'. Also, the bike is not to be capable of driving over 30mph to be considered a 'moped'. However, if it is not 'normally' able to go over 30mph and it is driven at normal and safe speeds, I believe this upholds the spirit of the law. You have the benefit of the bike not being thoroughly inspected before being registered. No one from the state is going to know that your pistons are bored out unless you perform something criminal.

"70 isn’t possible. The kid is probably looking at his TOMOS speedo which can be off by as much as 20 mph. 50-55 sounds more reasonable with that setup. Also, you can’t hit 70 really anyway since the tires are only rated up to 62 mph." -and they said man would never fly...

Many speedometers are always about 10% fast to make the owner believe they are traveling faster. This can be checked against police roadside displays. So, it is conceivable that at 30 mph, you're really going 27. Furthermore, radar guns rarely produce results more than +-5mph accurate. Conceivably, your speedometer could read 33 mph and you might still technically be street legal in a court of law. For God's love, don't hit anything. Elbow pads and gauntlets are not a bad idea. You'll like them if you fall. And leather is a reasonable protection against road rash. Excuses to look funky. Or funkier than normal.

Plus, guys and chicks, it is chilly out there. And whatever speed you're going will be added to windchill. Remember to wear the helmet. The head releases something like 50% of the heat you lose. That big brain takes a lot of blood, and blood carries heat and nutrients. Just like a well bored piston carries a lot of fuel. Rev that puppy. You might also do well with some leather jacket action, sweaters, longjohns, etc. Remember to dress in layers because the air pockets are good insulators and windbuffers. Don't get cotton wet. It will never dry and the liquid will cool you right down like a liquid cooled engine setup. Or freeze and then you'll have ice on you.

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