150cc cheap motor bike

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1. If there’s any one component that’s more likely to go out of adjustment on your scooter, it’s the carburetor. If it does go out of adjustment lots of things can happen. It can make the scooter hard to start, it can make the scooter slow to accelerate, it can cause the scooter to idle badly and stall or it can make the scooter idle fast so that it’s trying to go all the time and needs the brake to hold it stationary. None of these things are good.

   What the carburetor does is regulate the amount of fuel and air which are supplied to the engine. To go faster you need more fuel and more air and they must be in the right proportion. The fuel also has to be atomized as much as possible (i.e. be supplied in tiny droplets). The carburetor controls all these functions and generally does it quite well. Without removing and disassembling the carburetor, there are only two adjustments you can make, but these should take care of most minor problems. The first is the adjustment of the idle speed.

   Above is a picture of a typical GY6 engine carburetor and the view is that from the right side of most engine configurations on 150cc Chinese scooters. There’s a small spring loaded screw which adjusts the idle speed. It’s right next to the throttle control which is connected to the twist grip on the right handlebar. On most 150cc scooters, idle speed should be around 1500rpm when the engine is fully warmed up. Don’t make adjustments when the engine is cold. Take a 5 or 10 minute ride first. When the engine is cold the automatic choke is in operation and that can change the idle speed. If you have a tachometer, setting the speed is easy. If you don’t, you want to set the speed to a low idle. Fast enough so that the engine doesn’t stumble or stall, but slow enough that the clutch doesn’t engage and try to move the scooter forward. On most scooters from 50cc to 250cc, this will be somewhere in the 1500-2000rpm region.

   The other adjustment you can make is to the low speed fuel/air (“mixture”) ratio. This is done on most scooters using a screw adjustment on the other side of the carburetor as shown below.

   This screw changes the air to fuel ratio at low speeds. It shouldn’t need much adjustment, but the way to do it is to turn the screw very slightly (1/8th turn) and see if the idle speed goes up or down. If it goes down, turn the screw back 1/8th turn to where it started, then 1/8 turn in the other direction and see if the idle speed goes up or down. If it goes down, turn it back to where you started since you didn’t need any adjustment! If the idle speed goes up, continue turning the screw in 1/8th turn steps until the idle speed is at a maximum. If it starts to go down, turn it back to get the maximum idle speed.

   You may need to go back to the idle speed screw to lower the idle speed if it’s now too fast. So the basic procedure is to set the fuel/air mixture to give you the fastest idle, then use the idle speed adjustment to set the speed to the lowest rpm that gives you smooth running.

   If the scooter idles well and runs fine at low speed, but has problems at high speed, the problem may lie inside the carburetor with the main jet. The fuel/air ratio at higher speeds is set by the jets inside the carburetor and to get at them the carburetor has to be removed and disassembled. This can be a tricky job as the parts are small and delicate. The good news is that these carburetors are quite cheap. You can get a new one for $60-$80, so if you can’t make your scooter run smoothly and you don’t like the idea of taking the carburetor apart, you can always replace it!

   Comment by master — 05/12/2010 @ 3:15 pm

2. Scooters usually have a small engine, from 50cc to 250cc, though there are 400cc and even 800cc scooters, so engine size doesn’t define them. While most are limited in speed, scooters with a larger engine can exceed 100mph and cruise easily at freeway speeds, so speed isn’t a defining characteristic either.

   So what is a moped then? That’s a little trickier, but the working definition for most DMVs is a motorized two wheeled vehicle with an engine of less than 50cc capacity. It used to be that a moped was a Motorized pedal cycle, i.e. basically a bicycle with a small engine, but some jurisdictions don’t require pedals. Again we can also look at Wikipedia for a definition:
   Mopeds are a class of low-powered (under 50cc displacement) motorized vehicle, generally two-wheeled. A Moped is driven in an upright position with the rider’s back perpendicular to the seat . From a practical point of view, in most jurisdictions mopeds can be ridden without requiring a motorcycle license (a car license is sufficient). They may be speed limited by design, but even if they aren’t, the small engine size usually limits then to a top speed under 40mph (maybe 45mph downhill with a tail wind). In the United States the definition and regulation of mopeds differs from state to state. Again calling on Wikipedia:

   Legal terms and definitions of low-powered cycles vary from state to state and may or may not include “Moped,” “Motorcycle,” “Motorized Bicycle,” “Motorscooter,” “Goped,” “Motor-Driven Cycle,” and or others. A moped’s speed generally may not exceed 30 mph (48 km/h) on level ground, even if it is capable of going faster. In a few states this number is 20 or 25 mph (32 or 40 km/h), and in most states, the maximum engine capacity is 50 cc. However, Kansas (“Motorized Bicycle” K.S.A. 8-126, 8-1439a) allows up to 130 cc[13]. Some states, like California, require pedals, while others do not. Virginia allows mopeds to operate at up to 35 mph (56 km/h). Some states, like North Carolina, require there to be no external gear-shifting mechanism.

   Comment by master — 05/12/2010 @ 3:15 pm

3. Now you can look for “assembly instructions”, which with the average Chinese scooter will be one sheet of paper which says something like “attach the rear view mirrors, install the battery, etc.”. You may have to use some ingenuity to figure out how to do all this, but it shouldn’t be beyond the capabilities of any amateur home mechanic. It may help if you have a decent socket set, screwdriver set and set of metric wrenches since the supplied “tool kit” usually leaves much to be desired.

   Batteries are typically shipped “dry” with the acid in a separate container. You have to add the acid to the battery and leave it for 30 minutes of so before using it. After this it shouldn’t need to be charged to start the scooter.

   Once you have all the parts attached (and that will include at least mirrors, seat, rear carrier, battery and floor mats), and you’ve waited about 30 minutes after adding acid to the battery, you’ll be ready to start the scooter.

   If you just put fuel in the tank, you may have to crank it quite a few times before it starts since the fuel has to get to the carburetor and fill the float chamber before gas gets to the engine. You can prime the carburetor by disconnecting the fuel hose from the vacuum valve and connecting it directly to a small funnel and adding a little gas, then reconnecting the fuel line to the valve and adding fuel to the tank. However if you don’t know what you’re doing, just try to follow whatever instruction came with the scooter. Use premium gas. Most scooters seem to be setup to run on 91 octane fuel.

   The final point of assembly is to check everything. Check the tire pressures, check that every bolt and nut you can see is tight, especially the ones holding the exhaust and muffler – and the wheels! Look around for lose wires or rubber hoses that don’t seem to be attached to anything.

   Comment by master — 05/12/2010 @ 3:15 pm

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