08 crf250 r,leaking a lot of oil


I have a 08 crf 250 and a week ago I tear down the engine and i replace the piston ring with a 07 ring set. Since i change the ring i started to have some problems. When i ride for more than 10 min.The bike engine start to throught out engine oil by the breating hose filling the carb and the airbox with engine oil.

I dont know if this problem have something to do with the 07 ring set on a 08 piston,thanks

The rings should be fine...

Did you install the ring the right side up? There will be a little mark on the compression ring. The mark should be facing up. Did you stagger the rings correctly? None of them should be lined up with each other.

Next question. Did you break in the bike hard? if you didn't the bike will keep using oil, and you will get blowby, which in turn goes out of the breather.

the mark in the compression ring is facing up, and dont be lined.

i brake in the bike 10 minuts slowly 3thd and 4thd gear, before i ride hard ,i only change the rings. the piston have 13 hour of riding. i have i race this weekend i dont have a new piston kit

you another idea.

did you overfill the oil? Because if you overfilled it, the bike would be puking oil out into the airbox and into the crankcase breather.

One other thing: Your right crankshaft seal could be blown and your transmission oil is being pumped into your engine. The engine gets overfull due to this and then it goes out of the crankcase breather, and also makes its way to the airbox. Check to see if your trans oil is low.

I've got 19.4 hours on my 08, its been a great bike for me. I am putting in a JE high compression piston kit in at around 30-40 hours ish.

the firts thing that i do is check the oil level on both sides, engine and transmision, all is ok.

the qty of oil is big 200cc a 300cc, today i will disarm my top end and check evrything again.

i order a je piston kit 13.5 compression, but this coming the next week.

you have another idea why the oil is going out into the airbox and into the crankcase breather

thank you

Since your oil level is normal sounds like blow by. Double check that the oil control ring is installed correctly, end gaps staggered correctly and the expander ends not overlapping, also check the TOP ring end gap.

i found the problem,

the problem is that 07 ring set is totally different that 08 ring set, the 07 ring set is more thin vs 08 ring set.

thank you for your help

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