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CRF450R Leaking Oil out Exhaust

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Hey guys,

I have an 04 CRF450R and  I just got done re-building the top and bottom end on my bike. It has a brand new hotrods crank and a wiseco high comp piston. after about 4 or 5 short and easy rides I went to crank it up and noticed it was blowing smoke out the tail pipe. I shut bike off and the exhaust had smoke coming out of the pipe. I proceeded to go ahead and change the oil since that was on the agenda for the day...The oil was very dirty and was a light brownish grey milky looking color and immediately I tried to think of how any water or anything could have got in the oil but I haven't had it anywhere around water other than spraying it off after each ride which I always do. after changing the oil it stopped smoking and I rode it up and down the rode a few times and it suddenly started back. I shut the bike off and I could tell by the smell it was burnt oil...after trying to kick the bike several times it wouldn't crank back up and I noticed everytime I kicked it oil was leaking from the exhaust where the exhaust header and the muffler pipe connect..... after about 30 mins of pushing it back towards my house I got it started but it ran like crap the whole way home cutting out and sputtering....anybody have any input on what might be wrong????

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Is your cylinder in spec? An 04 could be pretty worn. Did you de-glazeyour cylinder or is it new/replated? There are ball hones for plated cylinders to clean them up. This will ensure the rings seat when you run it. 

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Is your cylinder in spec? An 04 could be pretty worn. Did you de-glazeyour cylinder or is it new/replated? There are ball hones for plated cylinders to clean them up. This will ensure the rings seat when you run it. 

The cylinder seemed to be in spec and in good shape I had a friend of mine who is a local mechanic do the re-build for me and I just helped out and he inspected the cylinder and was actually surprised at how good of shape it was in.

You rebuild the water pump new seals facing the correct direction? That would explain water in the oil but it's still passing the rings somehow. 

That's something I will have to check but like you said its still somehow passing the rings so my guess would be the problem is starting with the piston rings..

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did you install the oil scraper ring?

Honestly I couldn't tell you because I don't know much about these bike im new to them but we did install all the rings that came with the piston kit and like I said a motorcycle mechanic did it for me I just supervised lol and he does this stuff for a living so I trusted him but its definitely something I will ask him about...

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The appearance of cylinders can be deceiving. They should be measured with a bore gauge. Particularly in the area where the ring changes direction at the top of the stroke. You CANNOT eyeball a cylinder and determine its ok.

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It could be bad muffler bearings or seals that are letting the washer fluid out of the fuel tank and into the small pipey thing. It would probably burn off from the heat of the brakes and cause the smoke you're talking about.

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Also found out today when I tries to mess with it some that the kick start does not feel like it should its harder to kick and not very smooth???...it doesn't feel like it did when the crankshaft started locking up because then it only did it when it was warm but now its cold and hasn't ran and its not smooth and hard to kick......This is all weird because it seems that if we would have rebuilt something wrong it would have done this stuff right away not after several flawless rides.??

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