Dear Readers,
- Are you tired of cold starts? Need to raise the throttle everyday
to get the cold engine running?
- Does someone have the same bike as yours and are you tired of
losing to him in drag races?
- Suddenly, the fuel efficiency has reduced after a service?
- Has the 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.
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 ---
Every bike has a engine (motor/mill/muscle) and a carburetor
(breathing system/heart) ;) - Yeah 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.
--- This Guide Applies To ---
All the single cylinder bikes, 2 stroke or 4 stroke having a
carburetor. 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.
--- So Lets Get Started ---
Warm the engine nicely. Go get a ride around the town. Speedup 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 residential area 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 girl friend's
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. 2 stroke 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 - Carburetor]. 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 clockwise.
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.
OK the engine is humming perfectly, now what? Decrease the idle
setting screw to about 1000rpm in the tachometer. When the engine
slows down, just twist the throttle.
The response should be crisp and quick. It should not give any
hiccups! Try shutting off the engine and restarting.
The engine MUST start in a single kick or self with out giving
throttle. If this happens, the setting is ok. Now get a ride and
you'll notice the difference for good or bad :)
You'll immediately notice change in the engine sound and the
throttle response. Your engine can become more smooth or harsh.
Another important point is, Ride and Feel. Always take a ride and
get the feel of the bike in each gears, check the response and the
engine sound.
You'll quickly come to know once you get the feel of the bike that
you want to make the mixture rich or lean.
It may take a few iterations before you fix a setting as permanent.
Try calculating the mileage per liter and tally it with your
setting and the feeling you get.
--- Troubleshooting ---
Messed up your tuning because of me?
Here are some symptoms and their quick solutions:
Engine dies while tuning?
- Try the process all over again. This time set the idle screw
higher/faster.
Engine gives hiccups while driving, specially while in higher gears?
- May be the mixture is too lean. Try again.
Engine heats up?
- The mixture is too lean or too rich. Try again.
Whenever you race up the engine, the rpm increases fast but very
slowly comes down to idle?
- The mixture is not optimal, probably towards leaner side. Try again.
Too much low end torque and the engine sound is very beaty/thumpy?
- You'll face a low mileage surely, when you drive below 40kmph. You
have tuned on the higher/richer side.
I hope this helps! Take care.
- Are you tired of cold starts? Need to raise the throttle everyday
to get the cold engine running?
- Does someone have the same bike as yours and are you tired of
losing to him in drag races?
- Suddenly, the fuel efficiency has reduced after a service?
- Has the 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.
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 ---
Every bike has a engine (motor/mill/muscle) and a carburetor
(breathing system/heart) ;) - Yeah 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.
--- This Guide Applies To ---
All the single cylinder bikes, 2 stroke or 4 stroke having a
carburetor. 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.
--- So Lets Get Started ---
Warm the engine nicely. Go get a ride around the town. Speedup 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 residential area 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 girl friend's
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. 2 stroke 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 - Carburetor]. 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 clockwise.
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.
OK the engine is humming perfectly, now what? Decrease the idle
setting screw to about 1000rpm in the tachometer. When the engine
slows down, just twist the throttle.
The response should be crisp and quick. It should not give any
hiccups! Try shutting off the engine and restarting.
The engine MUST start in a single kick or self with out giving
throttle. If this happens, the setting is ok. Now get a ride and
you'll notice the difference for good or bad :)
You'll immediately notice change in the engine sound and the
throttle response. Your engine can become more smooth or harsh.
Another important point is, Ride and Feel. Always take a ride and
get the feel of the bike in each gears, check the response and the
engine sound.
You'll quickly come to know once you get the feel of the bike that
you want to make the mixture rich or lean.
It may take a few iterations before you fix a setting as permanent.
Try calculating the mileage per liter and tally it with your
setting and the feeling you get.
--- Troubleshooting ---
Messed up your tuning because of me?
Here are some symptoms and their quick solutions:
Engine dies while tuning?
- Try the process all over again. This time set the idle screw
higher/faster.
Engine gives hiccups while driving, specially while in higher gears?
- May be the mixture is too lean. Try again.
Engine heats up?
- The mixture is too lean or too rich. Try again.
Whenever you race up the engine, the rpm increases fast but very
slowly comes down to idle?
- The mixture is not optimal, probably towards leaner side. Try again.
Too much low end torque and the engine sound is very beaty/thumpy?
- You'll face a low mileage surely, when you drive below 40kmph. You
have tuned on the higher/richer side.
I hope this helps! Take care.
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