How to Increase Mileage of Royal Enfield
Will give you some Tips which will help you increase the mileage as well give you more or less perfect air-fuel ratio at idling.(different from tuning of the carburetor which involves adjusting the jet size etc).The carb in RE UCE is a Constant Velocity (CV) carb which meters the fuel intake.
The pilot screw is a small brass screw which is used to adjust the air or fuel intake into the engine.
Locating the Pilot Screw
1. Imagine that the carb is vertically divided into two sides : Engine Side and Air Filter Side.
2. Majority of the times, if the pilot screw is located on the engine side (as in this case), it meters fuel.
3. Hence, as in the image, if the pilot screw is turned clockwise -> mixture isleaner ( as it will stop the flow of fuel! duh!!)
and if it is turned anti-clockwise ->mixture will become richer (more fuel in!) :).
Leaner Mixture : More Air, Less fuel.
Richer Mixture : More Fuel, Less Air.
4. The effect of turning becomes opposite if the screw is located on the other side of the vertical i.e. on the air filter side.
Idling Screw :
This screw, as you can see in the image, is spring loaded and is connected to the throttle cable.
It basically controls the idling rpm. you can adjust the idling rpm by tweaking with the screw. (Generally it should be ~800rpm)
Adjusting the Pilot Screw of a Royal Enfield 350cc CV Carb:
Now that the location of both the screws is clear, we should start with the process of adjusting the pilot screw.
Disclaimer : PLEASE NOTE WHILE DOING ANY ADJUSTMENTS ON THE PILOT SCREW, IT IS A VERY FRAGILE AND DELICATE COMPONENT. THE TIP OF THE SCREW IS VERY FINE AND IT MAY BREAK AND GET STUCK INSIDE YOUR CARB IF OVER-TIGHTENED.
I AM JUST EXPLAINING THE STEPS TO IMPROVE YOUR MILEAGE, I DO NOT TAKE RESPONSIBILITY FOR ANY DAMAGES WHILE PERFORMING THE ADJUSTMENT.
SO PLEASE, TAKE PRECAUTION WHILE DOING THE FOLLOWING STEPS.
Step 1 : War up the engine. Preferably go for a 5-6km ride and check when the engine of your royal enfield 350cc bike is suitably warm.
Step 2 : Start your bike.The Factory setting for the pilot screw is ~3 turns out from the complete shut position. It should be around that. If not, not to worry. 🙂
Step 3 : Now, turn the pilot screw slowly clockwise so that it is going inside. Count the number of turns rotated. As you are rotating, you shall notice that the rpm of the bike is reducing and once you are near the complete shut position, the engine may die/stall. Completely shut the pilot screw, But remember DO NOT over tighten the pilot screw as it may damage the tip of the screw. Also, Remember the no.of turns rotated, as it is key to identifying the location of the screw for final adjustment.
Step 4 : If the bike has stalled turn the pilot screw anti-clockwise for letting some fuel in (~1/4 or 1/2 turn anticlockwise) and again start the bike.
Step 5 : At this point, slowly start turning the pilot screw anti-clockwise, you shall notice that the rpm is increasing. Continue turning until maximum rpm is reached. This is your ideal air/fuel mixture ratio at idle speed.
Also, if you keep on rotating the pilot screw anti-clockwise further, the rpm will again start to decrease. So it will be very easy for you to locate the ideal position for the pilot screw setting.
Step 6 : Count the no. of turns and remember them. It is generally lesser than what you started with before adjusting the screw, as the factory setting is tad bit on the richer side.
Step 7 : Take the motorcycle for a spin and you may notice the difference.
Richer Mixture gives low acceleration, low top speed and low mileage. It gives a smooth ride and high torque.
Leaner Mixture gives marginally higher top speed and high mileage. The ride offers low torque to play with.
Keeping your carb setting ideal gives you best of both and ultimately doesnt put a hole in your pocket!!!