Piston has seized - SOB!

I am so, so sad. My bike has broken down. My pride and joy has a seized piston. It sounds like a death sentence - and well, to repair it may as well be. It’s costing me an arm and a leg!
Why do pistons seize? What did I do wrong? I made sure the oil was changed every 1000 km’s and I took my bike to the repair shop whenever I thought it needed to go. (Sometimes I even took it when there was nothing wrong!)
My bike is a 125cc scooter, Kymco. I think it’s a 4 stroke and I’ve done 14 000 km’s on it.
I love my bike…

Did it have oil in it when it siezed? Silly question I know. Or were you using the correct oil?
It happened to me once. Apparently the oil had burned onto the piston and it had seized because of this. I got it fixed for 5 thousand NT.

I’m sure some of the motorheads around here will offer a much better explanation that me.

Sorry about your bike.

So how do you know it’s a seized piston? I often get a guy at a bike shop saying something pricey is wrong with my bike. I take it down the street and they tell me that guy at the first place was wrong.

The last time this happened, the guy told my wife that her starter needed to be replaced. It costs $1400 to replace the starter. I took it to the Bike Farm and he cleaned the carburator and also replaced a cracked air hose that was going to break some day soon. $500 total, and the scooter is starting fine now.

Anyway, assuming you’re right that it’s a mechanical problem, you’ve got another problem that is causing your scooter to overheat.

I’m sure it can be un-seized. Was it laying up for a long time? Did it seize at speed momentarily and then free up? (tends to throw you off that - but may not on a scooter I dunno)

I don’t understand how a piston can suddenly seize up unless it was overheating at speed. I would take it to Jeremy at Bike Farm as he will give you an honest appraisal.

The mechanic (which thankfully speaks fluent English) opened the bike up and showed the piston to me. We opened the piston up and he showed me that there wasn’t even a smear of oil inside it! Also, the bottom end of the piston, was welded tight onto the rod holding it and try as we may, we couldn’t get it off. Not even with a sledge hammer! Apparently the degredation of the piston had been going on for a while and other mechanics just didn’t take notice - I told them that the bike sounded wrong! There was a tick that grew louder and louder.
I’m sorry about the money I’ve had to fork out, but I love my bike and I hope it will be fine now.
Thanks for your replies! :rainbow:

Ah, there in lies the problem, perhaps. It may have been detonating, or ‘pinking’ due to wrong fuel, wrong plug, wrong air/fuel mix, wrong timing or any combo of those. The excessive heat may have cause some oil to carbonise, fall into the case and block one of the oil galleries…yadda yadda yadda.

Anyways, I hope they identified the cause of the problem, rather than just fixed the results.

Taiwanese mechanics don’t “fix” anything, they replace parts. They rarely do preventitive maintentance either.

No, that clacking sound is the engine telling you that there’s no oil (or that there was a shortage at one time in the past). There’s a common problem with that bike, the oil plug isn’t the right size. They tighten up so you think it’s all good, but it leaks and leaves you high and dry before your scheduled oil change. If it costs more than 5k you’re gettin jammed.