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The gearbox belt continues to come from pulleys

You mow with your riding lawnmower and it suddenly stops moving. The engine runs well and the lawnmower spins, but the lawnmower just does not move. You wonder what went wrong. A brief inspection reveals that the drive belt for the gearbox has come loose. You make the necessary maneuvers to get it back in place and again your lawnmower will move. A few minutes later the same problem happens. What are you going to do now? This is one of many frustrations in life, but can be remedied with a careful and conscientious following of suggestions in this article.

Belt condition

Examine the condition of the belt. Is it a twisted “floppy cloth”

;, or is it stiff and straight. Floppy belts need to be replaced as they continue to run off pulleys. If the belt has any twists or cracks, it must be replaced as when the twist or crack comes to a pulley, it will probably jump off the pulley. A belt that is stiff and straight can be used again.

gloved hand test engine transfer belt

The condition of the pulley

Check pulleys for rotation and straightness. If the castors will not rotate, they probably have the bearing and need to be replaced. Spring-loaded pulleys must be able to maintain the belt tension, so make sure that they can move freely on their turns. Tension springs must be connected at both ends to maintain the belt tension.

Pulley adjustment

Carefully check the alignment of the pulleys including the motor drive wheels, all idles, and the transmission (s) included pulleys. Yes, the Zero Turn mowers have two gearboxes that are usually driven by the same belt. Every up / down movement of pulleys will help to loosen the belt. If you find the pulleys misaligned, determine the cause. Once you have determined the cause of the pulley misalignment, you can fix the problem.

Transmission input disk

Check the tightness of the input plate fastener, as a flopping pulley will “throw” the belt. Make sure that the cooling fan integrated with the input disc does not come into contact with the belt and cause it to come loose from the pulley.

Gearbox points and bolts

toothed belt on gears and pulleys

Broken mounting brackets and / or missing / broken bolts will cause misalignment and in turn lead to the belt coming off the pulleys. Check the bolts carefully and tighten them as needed. Replace any missing or broken bolts. A good maintenance practice is to check all transmission mounting bolts at each oil change. The vibrations included in the riding lawnmower will loosen the bolts and the loads on the gearbox mounting points will cause them to break. Loose bolts will increase the error in the transfer brackets. Loose or missing bolts allow the gearbox to be tilted, which means that the pulleys are not aligned and causes the belt to come loose from the pulleys.

Engine bolts

Check that the bolts securing the engine to the mower frame are tight. If these bolts are loose or missing, it will cause the engine to go out of line and in turn, the belt may come loose. The vibrations mentioned earlier can loosen all bolts on the mower and cause misalignment. It is good practice to check all bolts for presence and tightness at a regular time interval or use.

Motor wheels and belt stabilizers

The engine pulley is held with a bolt upwards through the center of the pulley and threaded into the engine crankshaft.

engine crankshaft

If this bolt comes loose, the pulley will lower out of alignment and the belt will come loose. This bolt can fall out of the pulley and cause the pulley to come loose from the cutting motor. The motor wheel has some type of guide pins / belt stabilizers that help to keep the belt on the pulley. If these come loose or fall off, they will not be able to maintain the belt and pulley.

Get things back to the right position

Follow all the steps listed here and your lawnmower will work well and the belt should be in line with the pulleys.

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