Rebuild Time

[Paul Harris]

I rode at Dargle this weekend and the KTM ran beautifully all day saturday but seemed to be loading up on Sunday, then stalled and wouldn't start. Then seems to have lost compression and then stuck completely...

I think it was rebuilt and not used much before I bought it but there you go. Can anyone suggest the best source for engine parts - 1982 250MC? I got a lot of stuff from Bolton's when I built an '81 10 years ago but I had then motor rebuilt by a KTM dealer.

Cheers, Paul

[ozktm]

Rod kits and Pistons from Andre Horvarth or Al Beuhner.
Might only need top end, are you sure the air filter/boot was sealing and you didn't dust it?
If you can't do the rebuild yourself, I'll help out.

Adrian

[Paul Harris]

Hi Adrian. Pulled the top end off. The ring is jammed into the groove which I guess caused the loss of compression. The piston and bore are not too bad. The bottom end is jammed. There's a small piece of bronzy looking metal embedded in the piston crown. I'd appreciate any help - it's a great bike to ride!

You still in Wollongong?

[tony27]

I'd be suspecting the piece of metal in the top of the piston was part of a bearing cage if the bottom end is locked up

[Tony.Brown]

Sounds like the bearing cage broke up when the bottom end seized and pushed some of it up through the transfer ports to be mashed by the piston

[ozktm]

Time for a complete rebuild by the looks. Bearing cage failure as the other guys mentioned, gone up the transfers and pinched between the head and piston, hence why the ring is stuck...
You are very lucky to have trashed the cylinder.

[Paul Harris]

Seems 542 pistons aren't available anywhere. Would it be possible to adapt another piston?

[ozktm]

Buy the 541/540 type piston from the 73-81 bikes. They are essentially identical, but you then need to drill the holes for the reed to work.

[Paul Harris]

OK thanks for the advice.

[Paul Harris]

Got a rod kit from Andre - may be able to re-use the piston or a 3rd os is available or drill a non-reed one. Not sure if it needs a rebore - standard bore and doesn't seem to have ever been rebuilt. Sending to a very helpful bloke in Inverell to be done! It has a broken bottom fin above the clutch cable holder so I'll try and get that fixed or at least tidied up too. I suspect that might have been a dodgy enduro mod to give better access to the clutch cable. I'm really keen to do some vinduro on this bike!