Engine burning transmition oil

[gasser]

XC 250 engine burning transmition oil - burns about 8 ounces every 30 minutes. Spooge pours the pipe and bike smokes so bad you can't even see it (the bike) from behind. Oddly enough it doesn't foul the plug and still runs pretty strong. I've replaced the right crank seal but that didn't help so I pulled the top end and everything looked great. The cylinder was quite loose though and spooge was evident around the two front cyl. studs.
Anyone know how tranny oil is getting into the crank/cylinder area? This has got me stumped.

[Diddel]

Clutch side crank seal or tooth fairy.
Mine ran worse then when choke on and sucked 300ml in 30 mins ride time.

[blitz11]

How did the piston look?

A buddy's CR 250 broke a piston, holed the case, and the engine would suck trans oil through the hole. It didn't take much piston to hole the case.

You can make a pressure rig (plate over the exhaust and carb), pressurize the system, and listen/look for a leak.

blitz

[gasser]

The piston and the rest of the top end looks almost perfect and I changed the crank shaft seal but that didn't help.

[blitz11]

Nothing beats taking data to find the problem.

You might have a porous casting. Cracked case. Broken bearing boss.

The only way to find out is to pressure test the system and look for a passage in which the oil can be traveling. With a $5 Shrader valve and a couple of big rubber stoppers (or flat plates with neoprene gaskets), you can pressurize the system and find the leak. This is the only real way to find out w/o disassembling the entire bike.

As i mentioned in another post, my kid's ktm had a coolant leak. Turned out to be a porosity in the case by one of the rotary power valves. I had to make a rig to block off cooling passages, then a shrader valve on the cooling intake, then pressurize, and submerge the entire thing in the laundry tub. I could hear air, but i couldn't feel it.


In your situation, if it is sucking oil, you can pressurize the engine cavity, and then if the right side is disassembled, then you can look for the crack/leak with your ear or soapy water. once you find it, then weld/jb weld the problem, and you're in business.

Kind of a pain, but nothing beats data.

blitz

[GMP]

While Blitz's scientific approach is like mine, I have to suggest that you first check the o-ring between the crank sleeve and the bearing. While the sleeve rides in the seal, the o-ring is compressed and seals oil from leaking BETWEEN the crankshaft and sleeve, same setup on the countershaft.

This assumes of course that the seal replacement was done correctly.