79 DT250 siezed bottom end

[scroat]

bought the 79 DT250 on ebay, seller said hed recently rebuit both ends. rode it aound for a bit til one day as i was just idling round something went "ching ching ching..." and it stalled . it cranked hard when i tried to restart it- a raspy, dry metal sound. gingerly cranked it round when all of a sudden it freed up felt wet/smooth again and off we went.it did that and corrected again before the last ride... at the end of this ride i was pulling up and heard a similar sound . i pulled up and switched her off. after a call of nature i went to crank it round and it was stuck fast. nothing would move it-rollstarting just gave me a nice long skid, full jump kick, nothing. i pulled off the head and barrel, and piston- all unmarked . im waiting for the manual before i split the case. the seller thinks it might b a sheared flywheel key. theres some bits of metal in the bottom of the case. by turning the magneto and fwheel back n forth i can get it past the stuck point but it sticks again next go round. im new to bikes but cos i first felt it in the kickstart my theory is that the gear that engages with the box to crank it has come loose[circlip?] and its misaligned.ill know more when i split it but im worried about doing that b4 i get the book. what do you reckon?

[vintageguy]

could be a crank/rod bearing use the book

[scroat]

cheers mate, yeah ive got a fire under my arse waiting for the book. i'll post more when its split no doubt. happy trails

[AV8R]

sounds like the rod bearing on the crank siezed to me.

[scroat]

man this manual is taking forever
cheers tho'. will post more when im in the case

[scroat]

well, i was up in the shed today and looking at the motor waiting for the book etc.. and noticed for the first time that there was a small bolt kinda hanging inside the magneto! so i levered the magnet bit off and sure enough- solved... seems one of the three phillips head bolts that hold the baseplate of the magneto to the case had threaded badly, and fallen out. so now should i get a tap and some overszd little bolts, or can i helicoil a hole this small [app. 4mm]? the bolt had smashed a couple of the magnets- eventually chipping off a bit big enough to wedge real tight. hope this helps someone one day. i guess i wouldve noticed sooner if i had a magneto puller- i wouldve pulled it off first! but the only other magneto ive tried to get off bent my gear puller so i thought this one would be the same... happy trails. scroat