UPDATE: So i cleaned all the engine parts and also bought a new crank and SKF C4 bearings with crank seals. Rebuild the thing and started it up. Went on a test ride to also break it in a little bit. So far its done 200km and no issues so far (except that with the factory limiter it does 50kmh instead of the legal 25kmh). I didnt test the top speed just yet but it happily cruises at 70kmh. This thing is like a Bentley compared to my motorized bike! No vibrations, excellent brakes and plenty of power with the stock china CVT! Hopefully it will be reliable as its not pushing crazy power nor do i want it to.