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Just purchased a Gas Gas EC 250.

First ride out and bike would bog at full throttle , hoping that it would just clear up and kept riding , bike seized. Walked it home, took carb apart, and saw the dirtiest float bowl ever. Would this have caused the seize and bog  at full throttle?

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Sounds like a hard first lesson learned in pre-owned / 2-stroke dirt bike ownership.

Like many, I too have been there - done that.

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On 9/26/2019 at 5:32 PM, JohnFox1336 said:

Just purchased a Gas Gas EC 250.

First ride out and bike would bog at full throttle , hoping that it would just clear up and kept riding , bike seized. Walked it home, took carb apart, and saw the dirtiest float bowl ever. Would this have caused the seize and bog  at full throttle?

It could definitely cause that.  What year bike was it?  What Fuel:Oil ratio were you running?  Bogging usually means its running lean, which can be caused by clogged jets.  It looks to me like the bike was lean, and it melted down.  

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On 9/27/2019 at 3:23 PM, JohnFox1336 said:

Gas gas ec 250 recently seized pulled the plug and that’s what it look like. What can cause that, looks like piston smacked the plug

B50428BE-68DC-4269-B522-7D891BB7FD68.jpeg

5A15194A-FA12-4FB3-B8A8-A4B66BC4479B.jpeg

9E67C37E-85FB-4848-B2FE-B7FC6AEEEA9A.jpeg

That spark plug is the definition look of pre-ignition detonation (very bad). It wasn't just lean, it was very very lean.

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On 10/21/2019 at 12:35 PM, Jetster220 said:

That spark plug is the definition look of pre-ignition detonation (very bad). It wasn't just lean, it was very very lean.

And we have a WINNER!  🏆

When the OP pulls the head he will find the top of the piston scored and worn away as if someone had pointed a sandblaster at it.  IF he is lucky, there will not be a hole in the top of the piston.  Regardless he will need to decide if there is any chance of metal fragments in the crankcase and how lucky he feels with respect to not opening up the cases to clean out the crankcase area.

I had the exact same thing happen on our RZ350.  Even though the spark plug got arced across and stopped firing before the piston was holed, I still split the cases to ensure everything was clean in and around the crank.  The weird thing about the RZ is that they tend to only eat one cylinder.  Still not sure why.  One theory is that it is the result of an air leak through a crank seal.  Thus it is important to consider replacing the crank seals along with cleaning the carb to prevent a second occurrence.

When it happened to me I was WFO for several minutes and the engine was pulling well.  No bog, no obvious lean condition.  The other piston was perfectly fine and showed no signs of lean running. 

Edited by CDNSXV

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