cylinder head still good?

Hey guys,


  This is my first post, I hope I put it in the right place.  First off thank you all so much, I get a ton of information off you guys, and I hope to one day return the favor.  Getting to my topic, I have a 2000 cr250 that is / was running good before I took apart the top end.  I only took it apart because this is the third year I have owned it and I never have completed a top end job.  I took my cylinder to a local dirt bike service shop to have my cylinder measured to ensure that it is still in spec and has not oval out.  In taking it to the shop they did not measure it, just stated that the cylinder needs to be sent out to Millenium Machinery for resleeving.   The reason why they said this is because of a ring right below the cylinder head.  They stated the ring was caused by a lean condition.  I snapped a few pictures hoping to get a second opinion from someone.  I am okay with buying a new cylinder, I just wanted to make sure it really needs to go out.  Also I was hoping there maybe some other options, as in buying new or refurbished one off of e-bay or another website?  Are there other companies that can complete this for cheaper?





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I had this happen to my 125. The machine shop I took it honed the cylinder and the "ring" was gone. I'm not sure in your case but a good honing might take care of it.

Thank you, the repair shop I took my bike to stated they could hone the cylinder but they were in question on when the piston and rings would fail because of this.  The shop made it sound like it would fail before the next rebuild.  I don't know if there is any truth to this or not.  Also I tend to ride in national forest where if I broke down I would have an extremely long push to a fire road were I could drive a truck too.  So I am looking for reliability here.  I will be also tearing apart the bottom end.  My bike is starting to smoke black smoke more and more lately.  I did a leak down test and it pretty much dropped from 6psi to 2psi instantly, then slowly drop after that.  I was getting bubbles out of my crankshaft vent tube.  This would tend to make me think that the crank case seal has failed on my right side.  My compression was good at 183 psi, just 2 psi less than what the shop manual states it should be.  I think 185 is what the book said, but I do know it was 2psi less then recommended. 

do you stiull have this cylinder? dont get it "resleaved". that shop is a goony. its not even sleaved. its plated. from what i see ou can run a piston or 2 in there. just clean it. aslong as the plating hasnt rubbed off or chipped away, just clean it and slap a piston.


so many guys here likes to spend alot of cash saying they need to plate their cylinders after every top end. they also tell others to repalte their cylinders just like they do so taht they loose money. thats absurd. nikasil is very hard. it doesnt need maintaining all the time aslong as jetting is good and clean filters.


crosshatch there, its fine.

Soapy water and a scotch brite pad will clean it right up. Every engine I've ever had apart has a dirty ring at TDC, it is normal.

As long as there is nothing in the cylinder which you can catch a fingernail on, or deep vertical scratches, it is ok.

Also, black smoke and air out of the vent tube is probably right side crank seal, fix that first and retest.

Edited by mudguy

I already sent off the cylinder. I had someone else look at the cylinder and I did not mention I had already had it looked at.  He stated the same thing that I could get another couple of top ends out of it.  There were no scratches in it, his concern was that crosshatches were lacking in certain areas.  The piston looked clean and there was only one small area where blow by was present.  I did not mention the blow by was present on the piston to him, but he mentioned that if I looked on the piston I would probably see some.  So I trusted this guy and let him send the cylinder out.  He also looked at my crank and he showed me how one of the washers covering a bearing was burnt up and a different color.  He stated the crank needed to be changed.  So from what I read here factory OEM bearing and cranks are the way to go...  Are the best prices at  Also in looking at the diagrams there are a lot of bearing.  How do I know which ones I need?  Do I need all of them?  Is there another form on here with the bearings and seals that I need to buy?  I know crank seals are needed but unsure of which seals are the crank seals in the diagram (probably the seals located next to the bearings, next to the crank.)  Just hard to see the diagrams on the IPHONE.





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