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Oil Shooting From Exhaust cr250

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So I had bought a 94 cr250 a few months back on craigslist, rode it maybe 10 times and my bottom end had gone. I bought a kit on ebay of a wiseco bottom end with a namura top end. Upon teardown I found something previously scarred the old piston before I had owned it and that the connecting rod bearing within the crank went, causing the engine to seize. With help from the internet and my clymer manual I installed the new rebuild kit. Took my time, double checked things.. Torqued everything right, reassembled the bike. I had read of people using auto tranny fluid in their gearboxes so I decided i'd give it a go (Used valvoline full synthetic). Fueled it up 32:1 using amsoil interceptor. Went to fire it, started much easier than it had before. BUT.. Upon running it started burning mass amounts of oil, it bogged out two-three times, fired again started to run and the gearbox oil, ATF, started spurting from the exhaust. I assumed the ATF may have been too thin and was causing it to seep into the crankcase, I drained what was left of the old fluid and tried some 10w30 hoping it would solve the leakage. Fired back up ran much easier but the excess smoke remained as well as the oil leaving my exhaust (not as bad this time). I am certain I will have to open the motor back up again. This is my first bike, first time wrenching on a bike, I'm 18. Just before I dive back into it I'd like some opinions of others much more knowledgable than me. It's my opinion that the right halve crank seal hadnt seated correctly.. But any others feedback or two cents would be greatly appreciated! Thanks

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You are on the right track, either the ride side crank seal did not seat properly, OR the gasket that goes between the case halves is not sealing.   On the right side crank seal, did you put a new collar there, or just reuse the old one? Sometimes the collars will have a groove worn in them and putting a new seal against an old, grooved, collar will allow it to leak again.

 

There are also 2 rubber plugs that have to go in place when you bolt the case halves together. I can't remember if they would allow oil to get into the crankcase or not.. Maybe study your manual and see if there is any other way.

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Thanks for the fast response, I did install all the new bushings but I do have the old ones, too.. Should that collar be grooved what would my options be for that? That definitely isnt far fetched knowing it was raced backed in the day. I was wondering about the two sleeves, too that allow the case to seat together perhaps i should have put some sealer om those, dont think theyd lead to the crank, though..

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Ride side crank seal is gone.

 

Soon, that crank and piston will eat themselves as well.

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I was hesitant using the gasket given with the kit.. Just seemed to be cheap maybe I'd have better luck using a permatex type sealantI if such exists for bikes.. If anyone has experience with for the entire cas, or possibly a thicker gasket?

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You are on the right track, either the ride side crank seal did not seat properly, OR the gasket that goes between the case halves is not sealing.   On the right side crank seal, did you put a new collar there, or just reuse the old one? Sometimes the collars will have a groove worn in them and putting a new seal against an old, grooved, collar will allow it to leak again.

 

There are also 2 rubber plugs that have to go in place when you bolt the case halves together. I can't remember if they would allow oil to get into the crankcase or not.. Maybe study your manual and see if there is any other way.

 

 

Thanks for the fast response, I did install all the new bushings but I do have the old ones, too.. Should that collar be grooved what would my options be for that? That definitely isnt far fetched knowing it was raced backed in the day. I was wondering about the two sleeves, too that allow the case to seat together perhaps i should have put some sealer om those, dont think theyd lead to the crank, though..

This is the collar that the crankshaft seal rides on that kawabuggy is refering to from my 05' CR250 . Just after a complete engine rebuild i reinstalled it with a new seal , Smoked like a train. Ordered a new collar and seal , run like a champ. Also check your carb it may be super rich causing that bog also .   http://www.thumpertalk.com/topic/347305-is-your-two-stroke-running-rich-read-here/

IMG_1744.JPG

IMG_1745.JPG

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Why do I not remember that piece. Are those usually included in a bottom end kit or are they separate, I hadn't gotten one since I didn't know it existed. Lol maybe I oughta follow that manual more religiously..

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Why do I not remember that piece. Are those usually included in a bottom end kit or are they separate, I hadn't gotten one since I didn't know it existed. Lol maybe I oughta follow that manual more religiously..

There's your problem! LOL

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If you left that collar out, it is going to smoke like the dickens! The collar goes under the primary drive gear right on the right end of the crankshaft. You better pull the right hand cover and disassemble/inspect to be sure the collar is there, and that it does not have a groove in it. You will need to get back in there anyway to replace the right side crank seal so grab those tools and get going.

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Ohh...! The spacer piece behind the gear..(duh) Yeah thats definitely in there lol. Will check for wear, though.

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