⁉️Piston exploded! HELP!!⁉️

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Gashead24

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I have a chimera with a 30cc engine


I just bought this from a guy who said it had only been run a couple of times. I believe him, it was bought at Christmas and looks brand new. I drained the old fuel from tank and put my own gas in with a 25/1 mix, I used synthetic oil. He had it running for me and drove it around for 5 minutes before I bought it. It was running very rich and was bogging down. When I got home with it I drained his fuel and added fresh fuel and returned it to stock settings, 1 1/2 on H needle and 1 1/4 on L needle. I could still see his old fuel in the prime bubble, but I didn't drain it and figured it would be fine.


I started it up on the 2nd pull with choke off, I let it idle for a few minutes to warm up. I did 2 full throttle runs 100 feet down the gravel road. It was at full throttle for less than 5 seconds. I drove it closer to me at 1/4 throttle and when it got to my feet I let off the throttle, it idled and died. I tried to start it again but starter was jammed. I took it inside and disassembled it and took the motor out. Upon pulling off the head, I realized the bottom half of the piston had blown up into small pieces! There was no sign of wear or carbon buildup or stress on any other parts inside the engine!


Can anyone help me? I have no idea what would cause this catastrophic failure! I know I need to order a new piston and head gasket but I don't know if anything else has been effected. The crankshaft and cylinder head don't seem to be damaged.
 
The cylinder is probably trashed too. It could have been any number of reasons, but without inspecting the parts, it would be hard to speculate.
 
The cylinder looks fine. The bottom half of the piston had broken off at the arm. There is no other visible damage.

Does anyone know if there is a engine warranty of some sort?
 
Due to it having 2 different owners probably no warranty for it ...but you never know ! Do you have picks of the damages? They will want that for sure.
 
Yea I took pictures, but I don't have a photo bucket to upload them on here. Just pretty frustrating to have a basically new engine blow up like that. Now I'm SOL for bashing until I figure out what's going on. I did order a new piston and head gasket that should be here tomorrow
 
Yeah that does suck!! Some times its better to drop in a new piston and ring to start your ownership if the head is in good shape. Ya never know how hard people run things and say almost new
 
Yea that's true! Everything else looks good just needs to be cleaned up and make sure there's no residue of metal scraps left. Any recommendations of what to use to clean the small scraps out from inside the engine?
 
You have to completely break it down, man. The bearings in the case aren't sealed, and you want to make sure they're completely free of debris. If they feel crunchy when you turn them, replace them. I use carb cleaner to clean out the engines when I rebuild them.
 
Old post but let me shed a little light. When the piston arm was stamped in the die it wasn't at optimum temp hence the forming must have been incomplete and a crack fracture present which fatigued and failed.
 
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