I have an -90 XR250R. Yesterday I was out 2 hours and on my way home the engine suddenly died. Out of gas I thought, but no.

When I got and checked the bike almost all engine oil was gone. There is no sign of leakage. Oil plug is in place, all oil tubes are ok. I've refilled the engine oil.
The engine turns around without any problems, no strange noise.
I get a spark on the spark plug. Spark plug looks good, right color, but a bit wet since I've tried to start the bike. Air filter is clean. Carburetor gets petrol.
But I just can't get the engine to start?

Where have my engine oil gone?
And why doesn't it start?

/Regards Robert

Check ur kill switch lol
soz my world...:bonk: :bonk:

Hows the compression. Does it kick back a little or can you slowly push it all the way around with little force? You might have scored the pistin rings/cylinder enough to lower compression. Now it wont start unless its very warm or pulled by a car?

Refill oil to proper level and pull it behind a truck or car. Might start.

Finally got around tearing the engine down. Piston was totally busted.

There's a large piece of the piston missing, and I can only find lots and lots of tiny aluminum fragments in the engine.

I guess that explains where my oil went. Up in smoke...

Wonder what caused it. Probably just old age. Measured the piston to 72,4mm and the cylinder to 73,0mm. 0,6mm gap sounds way to much.

I think most of us have seen/experienced a piston like that unfortunately.
Good luck with your 270 project.[presuming 270, u may go bigger of course]
If you do go 270, and u happen to go with a 10.5-1 comp ratio and your bike has been gordoned and has a good muffler, then a starting point for you with jetting will be around a 120ish main, with a pilot of about 40.