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Cleaning lawnmower carburettors in an ultrasonic bath: getting your machines back on the lawn quickly

After the winter break, lawnmowers and ride-on mowers often fail to start. The problem usually lies in the fuel system: E10 petrol evaporates when left unused for long periods, leaving behind sticky resins. These sticky residues block the fine idle jets and internal channels in the lawnmower’s carburettor. If the resin also combines with fine grass dust and engine oil, a hard crust forms. The fuel supply is blocked and the engine refuses to start.

Manual cleaning in the workshop carries risks. Anyone who tries to flush out a gummed-up carburettor with brake cleaner or to clear the fine holes with a wire will damage the component. The hard metal scratches the soft, precision-machined brass jets. This alters the flow conditions in the carburettor, and the fuel-air mixture is no longer correct. At the same time, manual scrubbing ties up the mechanic’s valuable working time at the workbench.

An ultrasonic cleaner is the time-saving and component-friendly solution for professionals. An ultrasonic bath from Bandelin’s SONOREX series utilises the physical effect of cavitation. High-frequency sound waves generate microscopic vacuum bubbles in the aqueous cleaning solution. When these implode on the component, they mechanically blast away encrustations of dirt and resins. This process cleans the dismantled carburettor even deep inside the winding channels, where brushes cannot reach. The material is protected, the carburettor functions faultlessly and the repair time on the engine is reduced.

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Handling plastic mixing pipes and metal adaptors safely

Modern carburettors are made from a combination of functional materials. In addition to aluminium and brass, manufacturers are increasingly fitting plastic mixing tubes that are firmly pressed into place. These components are sensitive to solvent-based cleaning sprays. The aggressive chemicals attack the material and alter the dimensional accuracy within the carburettor housing. Cleaning in an ultrasonic bath using a suitable formulation such as TICKOPUR R 33 from Bandelin ensures the dimensional stability of the components.

The use of aqueous ultrasonic technology removes dirt from these material interfaces with pinpoint accuracy:

No wear and tear on materials: The soft plastic surfaces do not swell in an aqueous bath and retain their exact dimensions.
Physical cleaning: The high-frequency pressure waves dislodge the dirt through cavitation, rather than dissolving it with harsh chemicals.
Seams without any residue: Resin and engine oil are selectively removed from the narrow press lines between the metal and plastic, without damaging the components.

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Ultrasound cleaning

Achieving pressed aluminium lids and fine drill holes

The design of many ride-on mower carburettors conceals tiny channels behind tightly sealed covers. Ultrasonic waves penetrate the thin aluminium, as the metal conducts sound. Bandelin SONOREX units utilise the SweepTec function for this purpose. It generates a uniform sound field throughout the entire stainless-steel tank. This ensures that the cleaning power reaches every concealed borehole with the same intensity.

Prevent air pockets under lids

The chambers behind the covers are only cleaned when they are completely filled with cleaning fluid. A pocket of air immediately blocks the sound waves. The carburettor is turned whilst in the bath, whilst wearing gloves, until the cleaning fluid reaches every nook and cranny and no more bubbles rise to the surface. The switchable degassing function on SONOREX models degasses the liquid in advance, thereby speeding up this process.

Removing thick crusts of oil and grass dust

Mechanical pre-cleaning of the housing extends the service life of the cleaning fluid. Burnt-on layers of engine oil and dirt should be scraped off beforehand using a flat-bladed screwdriver or a wire brush. This reduces the amount of dirt entering the tank and shortens the dwell time in the tank. The sound waves then dislodge the last remaining residues from the pores of the aluminium.

Positioning floating-type trimmer carburettors correctly

Small, lightweight components quickly become buoyant in a liquid bath. Trimmer carburettors float to the surface as soon as there is any residual air in the cavities. Press the aluminium part beneath the surface and turn it until all the air has escaped from the cavities. If the carburettor sinks, it has become flooded. After the bath, the part is thoroughly rinsed with clean water to wash away any loosened dirt particles. The channels are then dried with compressed air.

Wear-free carburettor reconditioning for the peak season

Manually cleaning clogged lawnmower carburettors ties up valuable workshop capacity. Using a Bandelin SONOREX ultrasonic bath standardises this process and replaces mechanical scrubbing. Stubborn E10 residues and solid crusts of dirt are dissolved deep into the internal channels by physical cavitation, whilst soft brass nozzles and plastic housings remain intact. As a result, workshops significantly reduce their repair times per machine and ensure trouble-free engine operation without subsequent complaints.

FAQ – Cleaning a lawnmower’s carburettor

Why won’t the lawnmower start after the winter?

E10 fuel breaks down when left standing for a long time. The volatile components evaporate, leaving behind thick resins. These clog up the fine holes and jets in the carburettor.

Why does my trimmer’s carburettor float in the ultrasonic bath?

Air bubbles in the cavities create buoyancy. Turn the component underwater until all the air has escaped and the carburettor sinks.

Does ultrasonic cleaning damage solid plastic parts in the carburettor?

No, aqueous ultrasonic cleaners such as TICKOPUR R 33 do not damage plastics. The components do not swell and retain their shape. Solvent-based cleaners, on the other hand, cause damage to the material.

How do I clean the ducts behind pressed aluminium covers?

The ultrasound waves pass through the thin aluminium. The chamber behind it must be completely filled with liquid. Air pockets will prevent effective cleaning at this point.

Does the carburettor for the ultrasonic bath need to be completely dismantled?

Disassemble the component as far as possible. This ensures that the liquid and sound waves reach all concealed bores, thereby reducing the risk of air pockets. After the bath, rinse all parts thoroughly with water and dry the channels with compressed air.

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We - a Berlin-based family business in its third generation - specialise in the development, manufacture and distribution of ultrasonic devices, corresponding accessories and application-specific cleaning and disinfection preparations. The high vertical range of manufacture, a modern production facility and motivated employees distinguish us and are guarantors for constantly new quality products.