Update2: Thanks guys for all your ratings:)
It encourages me:)
Update: This review does not explain re-jetting or modifying your vehicle's Air-filter etc. This process still helps on a badly tuned machine or a stock machine.
Tuning your carburettor for optimal performance and fuel efficiency.
Hi People,
I am back after a looong time.
Are you tired of cold starts? Need to raise the throttle everyday to get the cold engine running?
Your gals brother has the same bike as yours and you are tired of losing to him in drags and races?
Suddenly, the fuel efficiency has reduced after a service? or Mechanic has screwed up your tuning.
Engine gives hiccups when you open the throttle?
Or your bike is just missing that smooth acceleration whenever you want?
Or your engine overheats even if you did not race too much.
Anything else which is not above;) and you just have the'kida'
May be the following will help you in tuning your mean machine for optimal power delivery and best fuel economy.
This guide aims at tuning the fuel/air screw to give you an optimal air-fuel mixture. An optimal mixture gets maximum performance from your machine.
Getting the basics:
I am assuming that you know driving very well and have completed at least 1000kms on road. If not, then you are too amateur to read this guide.
Every bike has a engine(motor/mill/muscle) and a carburettor(breathing system/heart);) - Yeh I know that. My point is, I assume that your engine is in perfect condition. That is, there is no oil leaking from it etc etc. The next assumption is that your engine is not DEAD. You know where your engine is and where your carb is;) and you have a screw driver/blunt knife with you. Your machine must have finished at least one service~500kms or more.
Also make sure you do not change the fuel type while tuning i.e. Power, Speed, Extra premium, normal unleaded etc.
To what bikes this guide applies:
All the single cylinder bikes, 2 strk or 4 strk having a carburettor. Tachometer is very handy and a must for a newbie or the tuning process will be very slow or painful or imperfect.
Disclaimer: Though whatever I have written here wont do any damage to your machine, finally you must not blame me for whatever happens. I am here to help if anything goes wrong.
So Lets get started.
Warm the engine nicely. Go get a ride around the town. Speed nicely at least upto half the top speed of the bike. Drive at least for 10-15 minutes so the engine system warms up nicely or you'll get a bad tune. Do not just leave the engine idle and start with process. I mean it. Ride the bike
Now that the engine is adequately heated up, you are ready to begin with the process. You can select a place far away from the city or your residentials so that you do not disturb the tired, sick, disgusted, old people or babes(babies) living in your colony. You are likely to be shooed away from them when you are at a critical point. You may choose a place near your sasoor's or would be girl friends house just to impress her.?
Put the bike in main stand and get hold of your screw driver. That is all you need, together with your eyes, brains and ears.
Searching the fuel/air screw
The above mentioned screws are responsible to adjust the air-fuel ratio which forms food substance for your engine. You can relate it to our human body, where proteins, carbs, fats, water etc all are required in appropriate proportions with respect to each other for good strong body.
There is another screw which sets the idle speed of the machine. This screw is not related to pickup or mileage. It just sets the engine rpm at'idle' run.
2stroke machines have an Air screw and 4 stroke machines have a Fuel screw. I hope you note this VERY well.
Air screw is located on the carb away from the engine. [ Engine - Carburettor - Air screw]
Fuel screw is located on the carb but its near the engine. [ Engine - Fuel screw - Carburettor]
If the make of your carb is Mikuni(Pulsar, Yamaha, Fiero.), the fuel/air screw probably will be of brass(golden colour.) If you fully unscrew this screw and take it on your hand, you will see a needle like tip.
Idle screw is closely linked with the throttle cable. Idle screw can be turned by the hand. Screw driver is not essential for it.
Finding these screws are very simple. If you still cannot find the air/fuel screw, ask your mechanic or I can help.
Ok now what? Apart from the above difference I gave between Air and Fuel screw, there is one more major difference.
Fuel screw turned in(clockwise) gives a lean mixture and turned out(anti-clockwise) gives a rich mixture.
Air screw turned in gives a rich mixture and turned out(anti-clockwise) gives a lean mixture.
Lean means more air, less fuel.
Rich means more fuel, less air.
This ends the basics.
Getting things in action
Turn the idle settings screw so that rpm reaches about 3000 rpm. Now tune the air/fuel screw to make the mixture leanest as possible. Please refer to the above whether you must turn the screw clockwise or anti clkwise.
As you make the mixture leaner, slowly the engine rpm decreases. Go on doing this until you have put the fuel screw to the leanest possible point. At the same time, ensure that the engine does not stall, by turning the idle-screw.
Tough huh? You'll get used to it;)
OK the engine is running and the mixture is lean
If you notice from the engine sound OR if you see the tachometer, the engine rpm will not be steady at this point. Now very slowly start turning the fuel screw anti-clockwise, quarter to 1/8th turn at a time. You will notice that the rpm increases slowly and steadily. Again, do this very very slowly. Also count the total number of turns as you wind out the screw.
You'll notice that when you have turned it to about 3-4 full revolutions, the engine rpm slowly becomes constant. It is this point that you must stop screwing more. This probably is the optimal setting for your engine.
Further on, try turning the screw even more and more to 5-7 revolutions and you'll notice that the engine rpm will slowly decrease. When this happens, you are just putting in a too rich mixture in your engine. At this point the engine loses all the fuel efficiency and the mixture is not optimal.
Repeat the process about 2-3 times. Count the revolutions each time and get the setting which you feel is correct.
Continued in the comments section
