Derestricting chinese geared 50cc motorcycles

On some machines there is a rev limiter in the cdi. However, unlike most scooters it is not a single wire going into the cdi unit. Therefore a complete new cdi unit must be purchased.

The easiest place to find them is to type in derestricted cdi on ebay and as long as its for a 50cc it should work unless its specified that it does not work fo your machine.

The next restriction is in the carburettor. Like scooters a smaller main jet is used to restrict the amount of petrol getting to the engine.

A bigger main jet needs to be used the best being jet no.90, but if you do this you must change the air fuel mixture screw accordingly and also a k&n style air filter is usually better but beware in the wet they absorb moisture and can restrict the airflow. Some companys sell socks for the filters to stop water getting in. I have never tried one of these so I cant review them sorry.

Most 50cc machines are restricted in the inlet manifold(the metal or sometimes plastic tube from the carburettor to the cylinder. A washer is placed in it to restrict the amount of fuel mixture getting into the combustion chamber. This can be simply removed however some machines have torx head bolts holding the manifold in place as a tamper proof attempt.

The fourth and final restriction I know about is the rear sprocket- this works like a push bike the bigger the faster acceleration the smaller the quicker top end but you must decide which one would be more beneficial to you. If you are constantly going uphill and are happy with a top speed of 35/40 on straights get the bigger sprocket, or if you mostly ride the flats and want a top speed of around 55 get the smaller sprocket.

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Comments 6 comments

Dennis A 6 years ago

I thank you for taking time in posting your comments. I have a FEIYANG 50CC scooter and the only thing like a CDI is I think called a ICU in the battery compartment. This guy was never connected. It has a 2-pin connector and a tiny brass screw but know not what the thing is for. I have looked all over for a Conventional CDI in my scooter and cannot find one. My scooter does not go past 20mph and coughs going up hill to 14mph. Changed, carb, cap and coil, sparkplug, cleaned air filter, whewwww don't know what to do next. Noticedthat when I put my hand over the air intake hose it has little effect on it running. Must be air coming in but have tightened down everything.

THanks for any responses. Have no one here to work on it.

Motor137 6 years ago

Regarding the post I just submitted as DENNIS A, you can also email me at I had not registered yet thus the different user name.



tarran 5 years ago

if it is a ped look for cdi in foot well

Rob Wurfel 5 years ago

Would try a valve adjustment tends to be a common problem

stephen 3 years ago


Jmac 2 years ago

Unscrew trap door in seat storage, loosen top bolt on carbeurator a bit. Idle adjustment

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