03 YZ450F Engine lockup! not cool!

2003 yz450f has had a new cp piston and rings(13:1), cam chain and pasted the valves for a fresh seal. put it back together and ran it for about an hour then i took it in the beach races, it went the best it has ever done never had it pull that hard. i stripped it down and touched up the frame, greased n cleaned everything. the bike sat for 12 or more months then i pull it out of the shed and took it on a forest trail for the arvo. the bike went good till the end after it got warm it was a hard to start and kept stalling worse then ever before. then at the end of the trail the bike started not idling and breaking down having *** moments. i check the carb nothing abnormal and the plug new. no change. then i took it out to another trail with a mate and after about 10 mins putting around and not idling i decided to give it a fang the in third gear it lock the back wheel and came to a stop. i took it home and tore it down to find the piston intake and exhaust side have marks in them and the wrist pin has mark on it. is there anything i should check for inside? the valves are all good nothing touched but the bike was binding up tight on the kick started? plz help!

Yet another thread that sounds like the rod bearing is seizing...

That would be my guess on an '03. Not an unheard of problem with that year.

Storing a bike for a year is an invitation to rust and corrosive damage to all of the bearings in general, particularly if the oil was not changed first.

will have a good look and i will also check out the oil pump as i think it may have lost oil pressure

The siezed rod bearings is probably whats wrong. Also, the oil pump wouldnt cause the marks on the piston in any way, shape or form. Another reason i love 2 strokes! :thumbsup:

Also, the oil pump wouldnt cause the marks on the piston in any way, shape or form.
Why wouldn't it?

i have found the lower con rod bearing notchy will be a full on split the cases. whats the best way to go now new crank assembly hot rod or a big bore kit or stick with the stock and run a high compression piston like i was(13:1)???????????????????

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