Cultus Carburetor air fuel mixture

[pwuser157223660331]

My cultus carburetor mixture screw needs to be fully tightened. Otherwise there is black smoke from exhaust. And unstable rpm on idle.
Other problem is if I press the gas paddle suddenly car proceeds with jerk as if engine stopped and then started again.
Mechanic says that this jerk is due to petrol reduction for good average.
Please guide me why mixture screw needs to be fully tightened? And this jerk problem?

[pwuser158913575038]

Do a carburettor service

[pwuser157223660331]

Got it serviced recently.
Problem is still there. Mixture screw is fully closed. It should be 2 1/2 turn loose.
What could be problem?

[naveedyu]

I think carby cultus doesn't have mixture screw. The screw behind the carburetor is to increase or decrease rpm.

[ZainMahdi]

It does have a screw - the actual screw has a rounded top and is enclosed inside a detached, freely spinning cylinder - you have to be a bit creative to adjust it.

[ZainMahdi]

I hope you mean fully seated - not tightened. Fully "tightened" as in desi-mechanic-gorilla-hands tightened means that your carburetor is ruined.

If its throwing black smoke at the fully seated position, then there is obviously something wrong with the idle circuit - could be a wrong size/damaged pilot jet or incorrect float level. Could even be something wrong with the ignition system.

Your mechanic said that the sudden "jerk" from instant throttle is from "petrol reduction"? He doesn't have the slightest clue about how a carburetor works then.

Find a proper mechanic, someone who properly understands carburetors (very rare, and he won't be cheap). Also, try reading and learning about carburetors from good source material - its necessary to owning a carburetor car these days.

[scholar.center]

You may use carby cleaner that may clean blocked air chanels inside carbeurator. I may help you. Air fuel ratio screw is rouned head and difficult to adjust.

[pwuser157223660331]

today I asked another mechanic. he said that mechanics when change the primary jet to small one they fully close the mixture screw.
another thing is that in my car external fuel pump is installed. this type...

[pwuser158913575038]

Why would someone do dis?

[pwuser157223660331]

According to them small jet will pass less fuel so average would be better.
When fuel pump stops working instead of installing new one there is jugarr by adding another external fuel pump in engine bay.

[pwuser158913575038]

So wrong. This jugarr is ruining our cars.

[ZainMahdi]

The average might be better, but the engine is starved for fuel - it will run under-fuelled and produce excess heat. The car will run like a malnourished donkey.

Please stop visiting these ustaads and listening to their jugaaroo science. There is a reason that those stock jets were installed by those who designed the car.

[pwuser157223660331]

I have bought Carburetor Repair Kit for 1150 rupees.
lets see what happens.

[pwuser157223660331]

I learned today that if mixture screw is fully seated it will use more fuel. by loosing the mixture screw more air and less fuel will burn. actually from mixture screw no fuel is moving through. it is air which is controlled by this screw.
correct me if I am wrong.

[pwuser151534747075]

Please tell me
Mixture screw required fully tight are some loose?
I have cultus 2006

[pwuser157223660331]

according to sf310 manual
PRIMARY SLOW SYSTEM
This system incorporates a solenoid valve which
opens the system circuit when the ignition key
is ON and closes when OFF.
Fuel coming through the primary main jet is
metered by the primary slow jet and mixed with
the air metered by the slow air bleed hole No. 1.
The mixture passes through the economizer jet,
is further mixed with the air coming through the
slow air bleed No. 2 and is discharged through
the bypass port and the idle port located near
the primary throttle valve.
While idling, the mixture is discharged mainly
through the idle port and mixed with the air
in the main bore. Therefore, the mixture ratio is
adjusted by the idle mixture adjusting screw.
That is, tightening it makes the mixture leaner
and loosening it makes richer.

1) Adjust idle speed to 900 (*950) r/min (rpm)
by repositioning (turning) idle speed adjusting
screw.
2) With engine idling at 900 (*950) r/min (rpm),
turn idle mixture adjusting screw to the right
or left and set it where the highest engine
speed is obtained. (This is the best idle position).
3) Perform above 1) and 2) once again, and then
readjust idle speed to 830 (*880) r/min (rpm)
with idle mixture adjusting screw.
4) Upon completion of the work so far, readjust
engine idle speed to the below specification
by turning idle speed adjusting screw slowly

[pwuser157223660331]

Iwhen car is idling. matlab slow per hu. then if the mixture screw is fully tight then engine should shut off.
if it is not shutting then idle speed is controlled by opening throttle plate by increasing idle speed through idle screw.
fuel is coming from primary system. plus bypass port.
you should decrease the speed of engine by loosing idle screw. and then adjust the mixture screw to highest rpm. it should be near 2 1/2 turns loose. after that slightly tighten the mixture screw according to service manual.

[pwuser165304945348]

Hi. Dear I purchased China carburetor for vxr. I adjusted it. Issue is that it through smoke when loosening the air mixture and doesn't through smoke when fully tighten. It never shut off in any condition. Butterfly screw is not turning to increase RPM. But still car is not shutting off in any condition. Fuel consumption is also not good. What will be the reason. I changed two carburetors for resolving the issue.

[pwuser170574928123]

plz change mixture screw, as i faced same