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Gunson G4125 Gastester Digital Portable Exhaust Carbon Monoxide CO Analyser

Features and Benefits:

Gastester is a digital exhaust Carbon Monoxide (CO) analyser with pulse pump that accurately measures CO levels for testing and setting carburettors (leaded or unleaded petrol) and petrol injection systems on any vehicle.
The digital display clearly indicates the volume percent of carbon monoxide so the engine can be tuned for optimal performance to run cleaner and more efficiently.
Ideal for checking CO after carburettor, ignition and air filter maintenance as well as tuning pre-cat classic cars, motorbikes and single cylinder engines.
The system is easy to use, a metal exhaust probe is held in place with a pair of retaining springs and a length of flexible pipe attaches the probe to the Gastester.
The kit includes everything needed for accurate CO testing and is supplied with full instructions.
A digital carbon monoxide tester for quick, easy checking of levels after engine maintenance work and tuning.
Calibrates in air, no moving parts to wear out and no filters to change.
Delivers accurate CO measurement to 0.5% at 15° to 25°C with adjustable calibration control for precise setting.
12V DC battery supply required.
Supplied with two core cables with clips for easy attachment to the car battery.
Contents: Gastester instrument including collector box and pulse pump/water trap assembly, metal exhaust probe with retaining springs, 3x flexible pipes and detailed instructions.
The Gastester only measures the CO level in the exhaust gas and is therefore not suitable for MOT and diagnostic checks or vehicles fitted with catalytic converters where an accuracy greater than +/- 0.5% CO is required.
FOR CALIBRATION - SEE IMAGE

Recalibration :

The easiest way to do this is-

Centralise the adjustment knob on the front of the unit by twisting it all the way left then all the way right. You should be able to get it roughly in the centre from feel.
Turn the unit upside down and take out the screw, the unit should now split in half. *make sure you put the top half in an upright position or the tool will not calibrate correctly*
Gently take off the face plate covering the PCB *DO NOT ADJUST ANY OF THE POTS APART FROM THE ONE IT THE PICTURE!
The pot you are about to adjust does the same job as the adjustment knob on the front of the unit just at a greater value.
Connect to tool up to a 12v battery and let it warm up for 15 mins in fresh air, remember the top half of the unit has to be in the upright position.
After 15mins adjust the pot in the photo with a screwdriver until you get to 2.0%. *let the tool sit for a 5mins then adjust to 2.0% again*
Put the unit back together, your tool is now calibrated and you should be able to adjust and use the tool as per the instructions.