What you'll do if your engine doesn't crank up? Many will look after fuel system and some after ignition system. Here, i'll try to list out some factors and things you have to check if your bike doesn't start. Here, the points that i'm going to list out will suit for carbureted bikes. I'll post a separate content for fuel injection bikes also. Let's go into the content.
Checking petrol tap
Firstly, you have to open the tank and see whether fuel is there or not. It might sound silly but mechanics face these kind of problems. Customers say that their bike is not starting without checking the tank. It happens not all the time but in very rare cases. So check for fuel. All the bikes without fuel injection have main and reserve petrol tap below the tank. The fuel flows from the tank to the carburetor via petrol tap with the help of tubes. Keep the tap in off position and unplug the tube from petrol tap to carburetor.
Use small container to store the fuel. Now turn the petrol tap to main or reserve position. If you see fuel coming from the tap, you can conform two things. There's no block inside the tap and there's no block in the tank breather hose. Then we can further with next step.
Checking ignition
Check for the sufficient battery voltage first. If voltage is acceptable, you can continue. If not, try recharging your battery or try to jump start. Remove plug adapter from the sparkplug. For doing this, you need a cutting player or any other things to hold. Hold the HT(High Tension) cable near the engine block. Turn on the ignition and try to start your bike. If you see spark, then the ignition system is working well and good. If you didn't see the spark coming, then you have to check for ignition coil, battery, CDI or TCI unit and ignition wirings. Then connect the plug with its adapter and now keep it near the block. Now try to start your engine. If you see very low spark intensity, clean the plug gap. Because, carbon particles will be deposited in the gap which affects the intensity. If needed, replace with the new one. Make sure that you are having a good plug adapter without any damage.
Checking carb and air filter
Even after checking the ignition and petrol tap, if the bike doesn't start, you have to remove the carburetor from your bike and have to clean it completely. Because, if there's any block in the jets, sufficient amount of fuel needed for the bike to start will not be sent to the engine. Make sure that there's no block in the breather hose of the carb. Because, if there's any block, fuel from tank will not enter into the float. If it is a CV carb, take care of diaphragm also. Next you have to go through is air filter. If the air filter is fully blocked, less amount of air will be induced for the combustion. Sometimes it isn't enough for the bike to start. So check the filters and replace if needed. Also check for any cracks or damages in the carburetor flange.
Compression
Remove the plug adapter first and also the plug from the sleeve. Slightly insert your finger in the plug sleeve. Make sure that you or not reaching the end. Try to start the bike now. By doing this you are slightly blocking the way. When you start, the piston forces the air out of the combustion chamber with some pressure. When that pressure comes to contact with our finger, we can hear a sound. If we didn't hear any sound, then the compression is very low and which is also the reason for not starting. Damaged gaskets or incorrect valve timing can cause these these kind of problem. If piston rings are damaged, then also the air escapes through piston rings to crankcase. This also may become one of the reason. If you face these kind of problems, head to the authorized service station.
Clogged muffler
If engine needs to start, your header and muffler should not be clogged up. Because the engine starts only if the entered air fuel mixture leaves the chamber through the muffler via header pipe. If there's any block in header pipe or in muffler, you need to sort it out.
These are all the important parameters you need to look after first. Now let's see some important secondary parameters.
Check for blown fuse
Old bikes have single fuse for all components. Some advanced carbureted bikes have individual fuses for individual components. So check the fuses. If you notice any blown one, replace it with a new one. If once again the fuse blows, you have some other problem in your electrical.
Check for any loose connection
Remove the seat and side panels to take a closer look at batteries. Check for loose battery terminals or weak or corroded terminals. Check the plug adapter for loose connections. Check ignition coil for any visible damages.
Checking petrol tap
Firstly, you have to open the tank and see whether fuel is there or not. It might sound silly but mechanics face these kind of problems. Customers say that their bike is not starting without checking the tank. It happens not all the time but in very rare cases. So check for fuel. All the bikes without fuel injection have main and reserve petrol tap below the tank. The fuel flows from the tank to the carburetor via petrol tap with the help of tubes. Keep the tap in off position and unplug the tube from petrol tap to carburetor.
Use small container to store the fuel. Now turn the petrol tap to main or reserve position. If you see fuel coming from the tap, you can conform two things. There's no block inside the tap and there's no block in the tank breather hose. Then we can further with next step.
Checking ignition
Check for the sufficient battery voltage first. If voltage is acceptable, you can continue. If not, try recharging your battery or try to jump start. Remove plug adapter from the sparkplug. For doing this, you need a cutting player or any other things to hold. Hold the HT(High Tension) cable near the engine block. Turn on the ignition and try to start your bike. If you see spark, then the ignition system is working well and good. If you didn't see the spark coming, then you have to check for ignition coil, battery, CDI or TCI unit and ignition wirings. Then connect the plug with its adapter and now keep it near the block. Now try to start your engine. If you see very low spark intensity, clean the plug gap. Because, carbon particles will be deposited in the gap which affects the intensity. If needed, replace with the new one. Make sure that you are having a good plug adapter without any damage.
Checking carb and air filter
Even after checking the ignition and petrol tap, if the bike doesn't start, you have to remove the carburetor from your bike and have to clean it completely. Because, if there's any block in the jets, sufficient amount of fuel needed for the bike to start will not be sent to the engine. Make sure that there's no block in the breather hose of the carb. Because, if there's any block, fuel from tank will not enter into the float. If it is a CV carb, take care of diaphragm also. Next you have to go through is air filter. If the air filter is fully blocked, less amount of air will be induced for the combustion. Sometimes it isn't enough for the bike to start. So check the filters and replace if needed. Also check for any cracks or damages in the carburetor flange.
Compression
Remove the plug adapter first and also the plug from the sleeve. Slightly insert your finger in the plug sleeve. Make sure that you or not reaching the end. Try to start the bike now. By doing this you are slightly blocking the way. When you start, the piston forces the air out of the combustion chamber with some pressure. When that pressure comes to contact with our finger, we can hear a sound. If we didn't hear any sound, then the compression is very low and which is also the reason for not starting. Damaged gaskets or incorrect valve timing can cause these these kind of problem. If piston rings are damaged, then also the air escapes through piston rings to crankcase. This also may become one of the reason. If you face these kind of problems, head to the authorized service station.
Clogged muffler
If engine needs to start, your header and muffler should not be clogged up. Because the engine starts only if the entered air fuel mixture leaves the chamber through the muffler via header pipe. If there's any block in header pipe or in muffler, you need to sort it out.
These are all the important parameters you need to look after first. Now let's see some important secondary parameters.
Check for blown fuse
Old bikes have single fuse for all components. Some advanced carbureted bikes have individual fuses for individual components. So check the fuses. If you notice any blown one, replace it with a new one. If once again the fuse blows, you have some other problem in your electrical.
Check for any loose connection
Remove the seat and side panels to take a closer look at batteries. Check for loose battery terminals or weak or corroded terminals. Check the plug adapter for loose connections. Check ignition coil for any visible damages.