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bottum end siezed after 5 hours

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Hi,

I have a 2004 KTM 125sx I recently got it fully rebuilt after a seizer and now its happened again after 5 hours. It was broken in fully. Basically I was 4-5 minutes into Weston Beach Race and the bike bogged down then locked up. After taking the head and the jug off I found the piston was okay but there was a lot of metal shavings and the bottom end had locked up I took some photos.  I have attached them to the thread. Does anyone have any ideas of what has happened?

IMAG0602.jpg

IMAG0601.jpg

IMAG0603.jpg

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It looks kinda tight and that thrust washer is bent...other than that i have know idea.

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Was the bottom end done during your rebuild?  Main bearings and the rod?  conditions when it seized?  Long straight @WFo then a sweeping corner where you chopped the throttle?  Did you jet the bike after your rebuild and for the sand race?  Bikes tend to like to run lean prior to a rebuild and have to be richened back up with a new top end.  Also in sand races I go up a few sizes on the main.  A 125 at sea level in the sand should need a damn big main in them (easily north of 200)

 

What is your jetting?

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Was the bottom end done during your rebuild?  Main bearings and the rod?  conditions when it seized?  Long straight @WFo then a sweeping corner where you chopped the throttle?  Did you jet the bike after your rebuild and for the sand race?  Bikes tend to like to run lean prior to a rebuild and have to be richened back up with a new top end.  Also in sand races I go up a few sizes on the main.  A 125 at sea level in the sand should need a damn big main in them (easily north of 200)

 

What is your jetting?

Hi, everything was rebuilt, bottum and top end at the cost off £400 not sure how much that is in dollars but he knew we was doing the sand race and he was meant to have jetted it for it. Conditipns  was damp, but I only got half way down the straight. We also done the gearing correctly aswell. 15 front 47 back for the mile long straight.

Thanks 

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Wow sorry to hear...  If I were you, I'd split the cases yourself and document each step.  Something wasn't done right, or wasn't replaced when it should have been.  Usually (not always, but usually) a top end would seize before the bottom if your jetting was too lean.  Its the shaving that have me puzzled.  Where did they come from and why?  You state the piston was fine... what about the cylinder and the head?  Is the piston needle bearing OK?  When the bottom end was rebuilt, what new parts were used,crank,crank bearings, seals?  

 

This is why I have learned (the hard way) to do all of the repairs on my own bike.  I know what was replaced, I can see if something is marginal and then make the decision to replace or not.  Can you tell us specifically what was replaced during the rebuild?  Why did it seize up previously?  

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ill guess amsoil. do i win a prize :smirk:

:lol:  :lol:  :lol:   ... but .. but ... but ... their OWN sponsored (and paid for by Amsoil) research paper says otherwise .... they have the BEST oil in the world.  A "secret ingredient" that nobody else has .. that's why I pay a fortune for it ...    :lol:  :lol:  :thumbsup:  :ride:

 

To the Op .. sorry to hear.  Did you use the OEM crank or a knock off ??  At least the jug and piston survived, which is good news :thumbsup:

Edited by supervokes

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It looks kinda tight and that thrust washer is bent...other than that i have know idea.

Appears bad crank install, shavings were the thrust washer. Too tight to one side, not centered correctly. And yes 200 or better but damp conditions would have kept it a little on the rich side anyway.

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what oil and ratio?

how much break-in time?

what were your break-in procedures?

Edited by terdog

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