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  #1  
Old 14-12-2016
clearasmud clearasmud is offline
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KTM125 mystery bag

I've picked up a 98 125sx that "went fine" and just stopped for no reason..

Diagnosis so far. Either the piston has been in there forever and decided enough was enough or it's hit the powervalve or both.. Thoughts ?
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  #2  
Old 15-12-2016
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Rebuild Rebuild is offline
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That's not mechanical damage, that's melted.
Maybe it was ridden without coolant?
Don't think it's detonation, as usually will have lot's of marking on crown too.

Check the bottom end for any movement up/down

How's the cylinder?
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  #3  
Old 15-12-2016
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ran too lean or held wide open for 30km's, maybe crank seals have gone.

as Rebuild said that's not a mechanical fault that's gotten too hot or too lean and melted the crown of the piston off, they may have got the ignition timing wrong also
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Old 16-12-2016
clearasmud clearasmud is offline
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Thanks for the input. Much appreciated. The cylinder had some black marks above the exhaust port but I've been able to clean most of it up so far with a honing wheel and a scour pad. No movement in the bottom end
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  #5  
Old 16-12-2016
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would have gone well just before it stopped though
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Old 16-12-2016
clearasmud clearasmud is offline
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To add some context here's the rest of it pre-tear down
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  #7  
Old 16-12-2016
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hmmmm not one of Ando's old bikes? Castrol KTM was the factory team in Oz at the time I cant remember who the 125 rider was on the team. Craig Anderson was the head rider for them most of the time. Danny Anderson was with them too but I think later on.

I hope your not going to leave that bore in that condition before you put it together are you?
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Old 16-12-2016
clearasmud clearasmud is offline
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No. Will take it to get cleaned up properly after christmas when i start the restore properly, that was just a quick scrub.
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Old 04-01-2017
clearasmud clearasmud is offline
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while im waiting for the piston to be delivered so i can send off the cylinder for a re-coat, i've hit the next challenge..
The upper shock bushing is knackered and I'm looking for a more economical alternative to the OEM one ( a lazy $197 for part 46811096s ), it doesn't look like all-balls make one. would this be a bearing shop item or am i stuffed ?
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Old 05-01-2017
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They're a spherical bearing I believe. Mite score em at bearing shop or could order one in. Maybe another brand crossover part(GG, husky, Yammy)
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