Motorcycle enrich our life, make it quickly and easily and expand our space.

But if you didn’t maintain the motorcycle well, it will also bring the

rider endless trouble and unnecessary economic losses. If your motorcycle

release colored exhaust when running on a flat road, it might have been

under serious illness. But you don’t need to be panic, stop the motorcycle

and watch the color of the exhaust. If exhaust is colorless or slightly

white, this suggests that your motorcycle is absolutely healthy. If the

exhaust is black, blue or rich white, then there is maybe some problem

with the motorcycle. If the exhaust is colorful or even there is dark smoke,

then there is something wrong with the engine and you need to figure out

the reason and repair it

The black exhaust

Black seems to be a depressing color. The reason should be rich mixture.

That is to say, the mixture of gas in cylinder component is beyond the

normal level. The incomplete combustion gas in the combustion chamber

cause the carbon particle exhausted with the waste gas.

Failure is likely to come from the following reason:

Air filter is blocked so there is not enough air input.

There is some problem with carburetor, like idling air inlet

congestion, then the air input is not enough.

The oil level of float chamber is too high, some gasoline go directly

into the cylinder without atomization, which will cause incomplete

combustion.

Main orifice wearout seriously and then the fuel injection from

primary nozzle increases, which will cause incomplete combustion.

Heating automatic valve is in start position and the enrich valve

can’t be closed automatically, which will caused a rich mixture.

Carbon deposit in muffler, exhaust jam, waste gas stay in cylinder,

which will caused incomplete combustion and then black smoke.

If the above failure is not eliminated promptly, that will lead to carbon

deposit at air valve, influnce the sealing of the combustion chamber,

decrease the engine power and low the speed. You should stop the motorcylce

immediately and clear the trouble.

Then you can follow the steps below:

Check whether the air cleaner is blocked or not.

If the filter element is made of paper, better to change the filter

element.

If the filter element is made of foamed plastic, it should be put

in kerosene or incombustible detergent for cleaning, then dryed,

and coated with a small amount of lubricating oil. Please note that

don’t put too much, otherwise it will reduce the air input. And

finally put the element inside the cleaner.

Confirm that there is nothing wrong with the air cleaner. Then check

the carburetor. For plunger type carburetor, use compressed air to

blow throuhg all the holes and tube so as to check if the position

of the main oil needle is right or not.

For those motorcyle with vacuum diaphragm type carburetor, you need

to check start heating automatic valve. Firstly, put the yellow

wires of start heating valve to anode of the battery and green wire

to cathode of the battery. Then, about five minutes later, connect

polyethylene pipe to fuel incremental loop and blow it with your

mouth, if the loop is full closed, there will be no ventilation;

If it can easily ventilated, which indicate the automatic valve

can’t close the loop, then you need to change the start heating

automatic valve.

The blue exhaust

Blue is a color of melancholy. If the exhaust is blue, you won’t be happy

too, which indicates that the engine oil is burning. This is mainly caused

by the following reasons:

There is a large clearance between cylinder and piston or valve and

valve guide, so there is more engine oil inside the cylinder. This

kind of situation mostly happened on those motorcycle used for long

year. So you need to check the clearance of the two places regularly,

so as to prevent excessive wearout.

When checking the clearance between piston and cylinder, you need

to pay more attention to the wearout of piston and piston ring. You

need to measure the diameter of the piston skirt and change piston

when it come to wear limit. And you also need to check and measure

the clearance between the piston ring, elasticity and light leakage,

and change the ring when it is worn, damaged or reach the limit.

Check the clearance between the valves and valve guide, you need

to pay more attention to the wearout of valve stem outside diameter

and valve guide inside diameter. Use the outside micrometer to

measure diameter of the valve stem when repairing, if it reaches

the limit, you need to change the valve. Before measuring valve

guide, the carbon deposit should be removed by reamer. The reamer

should rotate toward the right when taking it into or out of the

valve guide, otherwise, it will damage the inner of the guide. Use

the boredial indicator to measure inside diameter of the valve

guide, it is greater than the limit, then you need to change the

valve guide.

The direct cause of blue exhaust is the large clearance between cylinder

and piston or valve and valve guide, which is due to exceed wear of these

parts. So choosing the appropriate lubricant to prevent the excessive wear

of engine is an important way to avoid the blue exhaust. Be sure to use

qualified lubricating oil at ordinary times, you can choose it according

to operating manual of your motorcycle.

The white exhaust

White symbolizes purity, almost everyone can accept it. But when the

exhaust is thick white like milk, you should pay more attention of it.

Exhaust in thick white means there is too much water inside the exhaust.

There are mainly two reasons:

You have been fooled by gas station, there is too much water inside

the gasoline.

Or the problem is on your motorcycle itself. The channel gasket or

cylinder liner is damaged so that the cooling water come into the

cylinder.

Then there is too much water inside the gasoline, in addition of the white

exhaust, it will also cause exhaust pipe blasting or carburetor failure,

which will harm the engine.

You need to remove the gasoline which contain water in gasoline tank or

gasoline channel in time. Besides, if the channel gasket is damaged, you

need to change it promptly. And if the cylinder liner is damaged, you need

to find someone professional to repair it or even change it.