Scooter tuning dethrottling cdi?
Hey, I want to derestrict a Kymco Super 8 50 2-stroke via the CDI. I want to unplug this cable at the bottom. Does that deactivate the CDI? And everything is restricted to 25 km/h, even with spacers. Will I break the scooter if I deactivate the CDI? Because the throttle cable and D-ring are all restricted to 25 km/h.
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Two-wheelers with 50 cc are usually throttled like this:
*** CDI ***
The CDI measures the engine speed and shifts the ignition point when a certain speed is reached.
6000 revolutions should be about 25 km/h.
The tachometer is a magnetic sensor that records each revolution and transmits the data to the CDI.
Either this is located at the back of the variator, the counterpart, the sensor to which the tachometer reacts, is attached to the clutch bell.
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Or it is located at the pole wheel of the alternator.
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If this connection is disconnected, the CDI can no longer measure and therefore cannot throttle.
To find the right cable, you should have a wiring diagram of your scooter at hand and measure it with a multimeter.
For example, on my scooter the pickup is at the flywheel.
There are 2 cables connected: blue/white and green/white.
However, these two colors are also on the CDI connector.
So measure and look at the circuit diagram.
*** Throttle stop ***
The throttle stop is a small aluminum sleeve.
This sits above the spring in the carburettor and limits the travel of the carburettor needle so that it cannot go too high, meaning full throttle cannot be given.
To remove it, loosen the two screws at the top of the carburetor and carefully pull everything out.
Now you can see the sleeve with the carburetor needle, the spring on which the aluminum ring sits and the throttle cable.
The spring is pressed together so that the throttle cable can be unhooked.
Then you remove the spring to get to the sleeve.
Now simply push the throttle cable back through the spring, press the spring together and hook the throttle cable back in.
There is a groove on the sleeve with the carburetor needle.
There is a small pin in the carburetor.
The pin has to go into the groove, otherwise it won't work.
*** Spacer ring ***
The spacer ring is a steel sleeve that has been pushed onto the crankshaft.
This limits the path of the drive belt and thus throttles it mechanically.
To remove this, the nut on the crankshaft must be removed.
To do this you need either a locking tool to block the crankshaft, a ratchet with an extension and a lot of power, or an impact wrench.
It's much easier and faster with an impact wrench.
After the nut has been loosened, the fan wheel is removed, making sure to note where the washer and other things go.
Now the drive belt is removed.
Now the spacer ring can be removed.
Now put everything back on.
The nut has a right-hand thread!
This means that it is tightened to the right.
The crankshaft rotates to the left.
So it can happen that the nut comes loose at some point and can cause some damage.
Therefore, you wet the thread of the nut with threadlocker and then tighten it very tightly.
A master motorcycle mechanic explained to me that he tightens the nut with a torque of 90 to 100.
Before you start derestricting the scooter, it is imperative that you remove the spacer ring!
If this remains in place, the engine can over-rev, which can be very expensive!
The meaning of the generic CDI is the speed limit. If you leave it on cable pull, there will be little to remember – maybe 5kmh. It's not wild for the engine either. If you want more then see the answer from the Kaarster.