Piston ring failure, maybe 🤔

[Sherlock]

Over the past few months I have had to top up the engine oil on a regular basis with the right oil of course. Two weeks ago it was a lovely day for a ride out, checked the oil level and all ok. Set off through the village and all seemed fine until a wee hesitation in acceleration which cleared until another mile or so. Clouds of white/grey exhaust emissions and a prompt cut out of the engine. Parked up and let the motor cool off for a while but wouldn’t even turn over. So it’s on the bench waiting for me to decide whether it’s worth a full strip down and rebuild or bite the bullet and buy a second hand motor. Appreciate any of your suggestions.

 

[Ceesie76]

Seems like multiple problems to me; oil consumption points to general wear while the smoke points to coolant getting into the combustion chambers. If I were you I would look for a good used engine rather than looking for rebuild parts etc but if you do go the rebuild route then I suggest you compare parts prices between BMW and KYMCO, the original engine supplier. Good luck!

 

[sanoke]

I had a similar problem. I was riding my 2019 C400X when suddenly there was a loud clattering noise and a lot of blue/white smoke coming out of the tail pipe. The engine froze up and I had to have it towed to the dealer. Turns out it swallowed an exhaust valve. The problem was that the bearing for the rocker arm roller for the exhaust valves had worn to the point where the valve shim fell out. This caused rocker arm to press on the valve retainer instead of the valve stem. That caused the valve keepers to fall off and allowed the valve to fall into the combustion chamber. Fortunately I had an extended warranty so I got a new engine out of the deal.