In your vehicle, you are using Pelmag CNG Kit. This kit has 2 adjustment screws, as (1) Big Brass Knob - Idling Control and (2) Small Brass Knob - Sensitivity Control. This knobs are mainly use for idling control or low RPM. For high RPM, there is a Screw attached on the CNG Kit-Mixer hose. This is the Power Manual Screw for high-RPM or high-speed.
Melayunya skru yang besar pada regulator utk kawal idling (yang besar) dan yang skru yang kecik tu untuk finetune idling.
Here is the proper method to tune your carburetor CNG Kit.
(Please note that you should have proper device such as Air-Fuel Ratio Meter, RPM Meter or Gas Analyzer to obtain tuning accuracy).
Tuning HIGH RPM (for High SPEED)- Tuning with power Screw
It is necessary that you accelerate your vehicle to a CONSTANT 3,000rpm and hold it at that revv. Firstly, screw down the Power Screw until the engine starts to choke or the RPM drop. Quickly, reopen or screw up the Power Screw until you can notice that the engine start to ROAR or can easily achieve higher RPM. Since you do not have proper tools, you need to rely on the 'unprofessional' method of REV and HEAR, like most installers do.
Accelerate to 3,000rpm and hold. Screw down to choke the engine and reopen to allow engine Roar or ability to reach highspeeds.
The Power Screw controls the TOTAL VOLUME of gas for engine combustion. At 3,000rpm, the engines needs a lot of gas to combust for highspeed. Thus, you need to get the engine to come alive with the right volume of gas delivery, BUT NOT TOO MUCH or overconsumption. Too little gas with Power Screw Tuning, you should experience underpower or engine choke (jerking during driving).
Caution: Do NOT screw up the Power Screw until you have the bolt dropped out during driving. A member of this forum has openned the Power Screw until he lost it during his driving.
Tuning Low RPM (for idling)- Tuning with Gold Knobs on the regulator
Before you can tune, it is noted that most members of this forum do NOT have a special tuning tools. Thus, we can recommend a less-accurate but afford solution- USE Hand as the Feeling Device.
Place on hand on the Airfilter (Proton Iswara) or area that is NOT hot, but on the vibrating engine. Your hand should be FEELING the vibration. You should be feeling for NO vibration or Less-vibration.
Indicator: Vibrating - Bad, No or Less Vibration - Good or Better.
Big gold Knob - Idling Control or Tuning Base Idling
You should start with the black Knob. Turn the knob and feel the vibration. If it vibrates less, continue with that direction. Turn the knob with small turns (smaller the better). If turning the black knob brings big vibration, you should now progress with the Gold Knob or Sensitivity Control.
Small Gold Knob - Sensitivity Control or Fine-Tuning Idling
For fine tuning, you should use the small Gold Knob. Turning it will bring small vibration differences. Your hand should be feeling for smooth running engine vs vibration.