1. How to test capacitor inside single phase motor?
Discharge the capacitor. Set the multimeter to measure resistance. Connect probes to leads of capacitor. The meter will show a reading and soon will display an open circuit (infinity). Note down the reading that was displayed for that short period. Repeat the test several times. Every test should show similar result for a good capacitor.
2. Is it necessary to do the check spin once the wheel is balanced? 
Normally check spin (wheel off and on again) will give different result, most wheel balancer machine manufacturers permit tolerance 5g or even 10g. Because you can't position the wheel exactly the same as before, wheel balancer is metrological machine and it can sense tiny discrepancy. (Please contact us if you have more questions on this topic)
3. What are the recommended adaptor for balancing truck/bus wheels? 
Large size cone and large size backing plate can center truck/bus wheel.
Stud hole clamp is best option to fix commercial truck/bus wheel because it simulate the wheel on the vehicle. (Please contact us for if you need operation video)
4. How to properly mount the wheel on balancer in order to get good balancing result? 
Two key points: First use the hand to assist the wheel in straight position, not tilting on the shaft.
Second when the locking nut start to engage, rotate the wheel backwards while locking, this guarantee even locking force. (Please contact us for if you need operation video)

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