Piston shaft prone to seizing + conclusion to problem
1I live in a hilly area, stuck crankshafts can happen.
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Final decision on these problems: ordered new shaft, compression tester, and engine (to still have the ability to get back on the road incase of delays). All engines have no scoring, broken o rings or tears in the gaskets, no indication of DMG but evidence of uneven surface mounts, and stuck crankshafts or a broken pin on a crankshaft.
Diagnosis: 14k miles nt km on resistor spark plugs (to eliminate rich/lean fuel ratios, carbon build up and cvt timing belt problems) and 4k-8k on non resistor plug types in previous qmb engines before these shafts seize, vacuum leaks, bad luck etc etc. Can't repair two of the 4 engines, due to stock variator case epoxy welds but ordered a new one for a project scooter. The 2012 japanese peacesports should be the tester engine for the new shaft, should have one scooter running next week or 2 scooters running.
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The 2019 tao tao Scamazon vs the 2010 cy50 vs the 2012 peacesports vs the 2021 eBay motor replacement.
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Can it be repaired? 3 of these 4 motors can...but the tao tao may not be worth it due to uneven surface from factory build.
Turns out scamazons motor was NOT the worst of the three with bad oil pressure or oil seaming from the side ie incorrect seating of the oil bay housing. This caused oil to bleed from the side. It's possible to replace the oil housing with the the stock cy50s, then test it for compression but I can not access the cy50s stuck shaft. I knew this because the engine would never hot start and finally it would turn over too fast at full throttle when getting gas (Minor note the eBay motor has a stuck shaft just like the 2015 cy50). The cy50 is unsalvagable yet scamazon, peacesports and the eBay motor is salvageable making 3 of the 4 motors repairable.
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On a side note, why do I hate the taotao Scamazon stock so much so much? Easy, last time I checked it sped on idle after the hot start issues was given to me with a quality check sticker with meager 2000 miles driven. Yes, I remember swapping carbs thinking that was the issue, but there is a vacuum leak somewhere.