2 Stroke bicycle engine seized up, repair or total loss?

Algebruhm8

New Member
May 3, 2021
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I'm new to the whole motorized bike hobby and built my first one this Sunday, May 2nd, and ever since have been maintaining it and using it daily. Earlier today I was riding it as normal until I heard some loud metal click and started to lose power. I could still use it but it eventually died when I had to turn a corner and the back tire locked up. Had to carry it back home and opened the cylinder head to see that the piston had seized up. I took off the cylinder to reveal some deep scratches on the piston itself and the rings split open from whatever scratched it and it's impossible to move it up and down. Didn't lock up because of a lack of lubrication but the crankcase is definitely locked up. Checked the G-rings to see if any had come out and everything was in tack. I'm still confused as to what debris went inside that had caused this damage? I'm currently running a 16:1 ratio, no modifications to the engine, everything is completely stock and it ran perfectly until it locked up and seized. What I'm mainly looking for is potentially a refund if at all possible or at least some replacement parts although having to split the case open and repairing it is outside my expertise and wouldn't seem worth the time, money, and labor to fix it up if it's going to come near the cost of what I paid for ($230 for the whole kit). Here is what the piston looks like. Looks horrible in my opinion.
 

Algebruhm8

New Member
May 3, 2021
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The piston is history, how does the cylinder look? Is it gauged too? Are you saying that the crank won't move at all?
Oddly enough the cylinder is in perfect condition. Crank won't move a centimeter tho. Everytime i try to engage the clutch the rear tire is solid and will just skid on the floor. Looks like some debris digged through the piston down to the crank which must've caused all sorts of damage to the crank.
 
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Tyler6357

Well-Known Member
Mar 15, 2012
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Santa Barbara, CA
Are you sure there isn't like part of one of the rings in there locking it up? If you can get the crank to move fixing it would only cost you maybe $25-$30, however, if the crank is damaged, it might be just worth it to get another engine. Where did you get it? Maybe they will take it back if it hasn't been too long since you got it.
 
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Algebruhm8

New Member
May 3, 2021
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I believe so that one if the piston rings may be stuck in there. I'm just hoping it hasn't caused damaged to the crank but it's very likely. The website i bought it from is Bikeberry and I'm trying to see what they can do about it but this is mainly why I dislike ordering products outside of Amazon, poor customer service and very hard to return items without writing an essay to convince them to give you a refund.
 

Tyler6357

Well-Known Member
Mar 15, 2012
1,285
288
83
Santa Barbara, CA
I believe so that one if the piston rings may be stuck in there. I'm just hoping it hasn't caused damaged to the crank but it's very likely. The website i bought it from is Bikeberry and I'm trying to see what they can do about it but this is mainly why I dislike ordering products outside of Amazon, poor customer service and very hard to return items without writing an essay to convince them to give you a refund.
Ha! I understand about bikeberry. If you have one of those magnet antenna tools you could maybe fish it out or maybe you can remove the engine from the bike and turn it upside down and shake it out. You should remove the piston by taking the wrist pin clips, wrist pin and needle bearing off. Are both of the clips still there? You need to get the crank spinning again. If you do that, you can replace the piston, rings, needle bearing and clips, if you need them, and maybe the head gasket. These little engines are not very complex and are usually easy to fix (use youtube videos if you are not sure) , you can get parts cheap on e-bay. But if you can't get the the bottom end fixed good, and get the crank spinning, I would recommend sending it back if it's still within the warrantee period, you followed the directions, it sounds to me like either a ring broke and got run through the cylinder or maybe one of those wrist pin clips, which is a very common thing to have happen. They don't always assemble these things correctly. Bikeberry knows this.