Seized MS290?

[kyle23]

Good morning, I have a MS290 that recently seized up. Went to pull the starter rope and it pulled a few times then locked up. I pulled the recoil assembly off and it pulls freely, pulled the flywheel to see if there were any obstructions behind it and nothing. Pulled the exhaust and this is what my piston looks like. I did recently install a new 390 piston and ran a few tanks of fuel through it. Any insight on where to go next? Any help is appreciated thank you.

 

[coffeebrk]

Did you do pressure and vac test before installing the piston?

 

[pioneerguy600]

Is it locked up solid, did you try turning the flywheel by hand? If it is solid locked could be a circlip has come loose, very probable if the new piston and cylinder were AM and even OEM ones can come out if not properly orientated when installed. If a clip gets thrown out the piston pin can walk out and get stuck in a transfer port.

 

[irhunter]

Any insight on where to go next?View attachment 1216644

Simple: open it back up. See what the deal is.

Roy

 

[Wood Doctor]

Rotten luck. You may have gotten a lousy replacement 390 top end kit. Perhaps just try again and rebuild with a different brand. I must agree with PioneerGuy600 that a circlip may have come loose. That happened to me once, about seven years ago.

 

[J D]

As mentioned, you need to check those circlips... you may have gotten very lucky if one has come out!
Did you work out what caused the demise of your last top end? That looks like way too much piston wear for just a few tanks... I'd suspect it's either tuned lean or you have an air leak as well