Sounds like a timing problem(flywheel key) sometimes the key will shear part way do to wear, flywheel key is located on crank end under flywheel, disassemble air housing to expose flywheel crank nut unscrew nut (impact) to see key and keyway slot in crank determine that key is not sheard and is in center of crank keyway slot. if sheared you will have to use a puller to remove flywheel from crank. install new key and reinstall flywheel with an impact gun .
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Sounds like a timing problem(flywheel key) sometimes the key will shear part way do to wear, flywheel key is located on crank end under flywheel, disassemble air housing to expose flywheel crank nut unscrew nut (impact) to see key and keyway slot in crank determine that key is not sheard and is in center of crank keyway slot. if sheared you will have to use a puller to remove flywheel from crank. install new key and reinstall flywheel with an impact gun .