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Troubleshooting

A5 engine problems

Engine doesn't start

Step 1: Is there fuel in the carburetor?

Disassemble the carburetor float chamber and check for fuel in it.
>NO
Check Possible condition Remedy
1. fuel hoses leaking/broken replace
2. carburetor filter dirty/clogged clean
3. fuel tank filter dirty/clogged clean
4. fuel tank empty/low level add fuel

Restart the engine. If problem persists, go to Step 2.
>YES
Check Possible condition Remedy
1. fuel tank dirty fuel replace

Restart the engine. If problem persists, go to Step 2.

Step 2: Is spark OK?

Unscrew the spark plug and connect it back to the plug cap. Insert the spark plug between two cylinder head cooling ribs so that the outer ring touches the ribs. Now kick the starter a couple of times and observe the spark. It should be blue and strong.
>NO
Check Possible condition Remedy
1. spark plug see spark plug condition table replace
2. plug cap no contact replace
3. electronic ignition coil faulty replace
4. primary coil faulty- check resistance replace

Restart the engine. If problem persists, go to Step 3.
>YES
Go to Step 3.

Step 3: Is compression OK?

Push the piston to TDC and remove the carburetor. When blowing into the crankcase through the intake manifold pressure should form.
>NO
Check Possible condition Remedy
1. thermal unit gaskets air leakage replace
2. piston rings worn-out, broken replace
3. piston worn-out, burned replace
4. oil seal worn-out replace
5. reed valve broken, leaking replace

Restart the engine. If problem persists, visit a repair shop.
>YES
Visit a repair shop.

Engine stops or runs irregularly

First check if the choke is closed. It should be open and should work normally.

Step 1: Fuel check

Check Possible condition Remedy
1. fuel presence of water replace fuel
2. carburetor dirty, clogged clean/replace
3. fuel hoses leaking/broken replace
4. fuel tank filter dirty/clogged clean
5. fuel tank empty/low level add fuel

Restart the engine. If problem persists, go to Step 2.

Step 2: Spark check

Check Possible condition Remedy
1. ignition incorrect timing adjust
2. spark plug see spark plug condition table replace

Restart the engine. If problem persists, go to Step 3.

Step 3: Is compression OK?

See above.

Engine power loss

Problem of this type occurs mostly because of three conditions:
  1. Carbon deposits in exhaust port and exhaust pipe due to use of low quality two stroke oil or after a long period of operation; decarbonize the exhaust pipe and clean the exhaust port.
  2. Air filter is either dirty or clogged; clean or replace it.
  3. Engaged brakes; grease the brake cables.
If problem persists, go to Step 1.

Step 1: Fuel check

See above. Restart the engine. If problem persists, go to Step 2.

Step 2: Spark check

See above. Restart the engine. If problem persists, go to Step 3.

Step 3: Is compression OK?

See above.

Transmission problems

First make sure that you are using correct transmission oil type (ATF Dextron III).

Clutch doesn't engage (mainly in cold weather):
Restart the engine and add power slowly (transmission oil is probably cold and dense).

Engine shakes during acceleration:
Transmission oil level in gearbox is too low - add oil.

Clutch doesn't shift from 1st to 2nd gear:
Engine power loss (see above).
Transmission oil level in gearbox is too high.
Blocked clutch - try to engage the clutch by adding power while moped is on the center stand.

Clutch rattles while shifting into 2nd gear:
Chain loose - tighten the chain.
Transmission oil level in gearbox is too low - add oil.

Other common problems

Braking efficiency decreases (loose braking handles):
Gradually but not completely unscrew the adjustment screw on the braking handle to adjust the brake lever movement; pay attention not to block the wheel rotation.

Throttle handle turning becomes hard:
Replace the throttle slider located in the throttle twist tube and grease the throttle cable.

CEV rev counter problems (AT/BT 50)

CEV rev counter Many riders have reported CEV rev counter issues involving inaccurate readouts and dead counters. Reason for most of these problems are voltage peaks in the electrical system of the motorcycle. These put a lot of stress on the 21 Ohm input resistor of the counter electronic circuit which may and most often do result in overheating and failure of the resistor. You can easily and efficiently solve the problem by replacing the stock 1 Watt resistor with 5 W ceramic resistor.