RPM reading not constant

2003 Honda Dylan SES 125 Scooter Engine ebay - YouTube

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https://www.youtube.com/watch?v=DzAByfS2OAY
Nov 21, 2012 - Uploaded by TheShamefulsin
Short video demonstrating a 2003 honda dylans engine, that it starts and runs for the purpose of selling the ..

honda dylan in United Kingdom ' Motorbikes & Scooters for ...

https://www.gumtree.com/motorbikes-scooters/uk/honda+dylan

GumtreeMy 2003 Honda Dylan ses 125, unfortunately it was stolen from me, hence the .... uk plate GF07 XJK,bike has only few scratches, last time I could not start it, but ...

indicates an electronic unit failure from internal shorting and overheating
could be the (ECM)control unit or coil/sif not electronic control , then the ignition module

Check that the exhaust wasn't damaged in the crash. The exhaust on modern restricted motorbikes is a big part of the correct running of the engine.It could also be the induction system rubbers, If it is not fitted properly the extra air into the engine will change the power characteristics.

The unit in the bottom of the float bowl is an anti fire solinoid, when the ignition is switched off a small needle is inserted into the main jet in the carb, the idea is to stop fuel entering the engine as the engine shuts down, if fuel enters the engine as it is shutting down it is sent out the exhaust valve and into the hot exhaust, this in turn can and does cause a massive bang, you can test this by removing the unit from the bowl, switch the ignition on, the centre needle should retract into the units body, if not it is bad and will stop the engine from reving.

that is a check engine light.

Check Engine light is on
The engine computer or PCM/ECM

All modern vehicles have a computer or the ECM (Electronic Control Module) that controls the operation of the vehicle powertrain (the engine and transmission). The main purpose of this is to keep the engine running at top efficiency with the lowest possible emissions. With constantly growing demands for better fuel economy and new strictest emission regulations it's not very easy to achieve. The engine parameters need to be constantly and precisely adjusted according to various conditions such as speed, load, engine temperature, gasoline quality, ambient air temperature, road conditions, etc. That's why today's cars have much more electronics than in early days - there is a large number of various sensors and other electronic devices that help the vehicle computer or ECM to precisely control the engine and transmission operation and monitor emissions.
The vehicle computer system has self-testing capability. When the computer senses that there is a problem with some of the components it stores the correspondent trouble code(s) in its memory and lights up the "Check Engine" or "Service Engine Soon" light to tell you that there is a problem and your car needs to be looked at. To properly diagnose what is wrong, you need to take your car to a mechanic or a dealer. The technician at the dealership or a garage will then hook up the scanner to the car computer and retrieve the stored trouble code(s). Then he (she) will look it up in the service manual provided by a car manufacturer. The service manual contains the list of possible codes (about few hundreds) and describes what each code means and what needs to be tested. The code itself doesn't tell exactly what component is defective - it only indicates where to look, what engine parameter is out of normal range. The technician will have to perform further testing to pinpoint a defective part.

please read this about your check engine light.

Why my Check Engine light comes on? The engine computer or ECMAll modern vehicles have a computer or the ECM (Electronic Control Module) that controls the operation of the vehicle powertrain (the engine and transmission). The main purpose of this is to keep the engine running at top efficiency with the lowest possible emissions. With constantly growing demands for better fuel economy and new strictest emission regulations it's not very easy to achieve. The engine parameters need to be constantly and precisely adjusted according to various conditions such as speed, load, engine temperature, gasoline quality, ambient air temperature, road conditions, etc. That's why today's cars have much more electronics than in early days - there is a large number of various sensors and other electronic devices that help the vehicle computer or ECM to precisely control the engine and transmission operation and monitor emissions.
The vehicle computer system has self-testing capability. When the computer senses that there is a problem with some of the components it stores the correspondent trouble code(s) in its memory and lights up the "Check Engine" or "Service Engine Soon" light to tell you that there is a problem and your car needs to be looked at. To properly diagnose what is wrong, you need to take your car to a mechanic or a dealer. The technician at the dealership or a garage will then hook up the scanner to the car computer and retrieve the stored trouble code(s). Then he (she) will look it up in the service manual provided by a car manufacturer. The service manual contains the list of possible codes (about few hundreds) and describes what each code means and what needs to be tested. The code itself doesn't tell exactly what component is defective - it only indicates where to look, what engine parameter is out of normal range. The technician will have to perform further testing to pinpoint a defective part.

THE COOLANT LEVEL IS LOW

on the older hondas even the newer ones idle speed is coolant temp controlled.

when the engine idles up the electronic coolant temp sensor is submerged in coolant and reads warm, so the engine computer idles the car down. the coolant level if low than drops from around the coolant temp sensor and it says the engine is cold, so the engine computer idles the car up.

which results in the constant rise and fall in engine rpm.

ADD COOLANT TO THE RADIATOR AND WATCH THE CAR MAGICALLY FIX ITSELF.

if your bike likes to wander at high speed these fork braces can help.
how ever do some research on the manufacturer of the brace to make sure it is of good quality



hope this helps

Change the fuel filter. the light comes on when your not getting enough fuel presure.