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08 XR650L Piston Ring Replacement

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Hey again, thanks all for helping me get my bike back in order but I might need some more advice.

I recently re-did the top end, valves, cam swap etc. and after I got it revived it was smoking on cold starts but stops smoking when the engine gets at operating temp. It's not a TON of smoke, but it is embarrassing when I'm leaving work or a friends house and I have to smoke out the neighborhood before I ride off. My experience with this in the past is oil in the combustion chamber burning. My guess is the piston rings need to be replaced, or it needs a complete bore job.

My question is: What are the tolerances for stock rings VS needing to do a bore job?

 

I'm still riding right now until I can get the $ to buy new gaskets and rings and whatever else it may need, so I don't have the diameter of my cylinder or piston at the moment. 

(Secondary thought: When it did not smoke, prior to top end rebuild, it had very old and viscous oil. When I did the rebuild I did an oil change with fresh oil. Could the thinness of the new oil be enough to seep past the piston rings when the viscous oil wouldn't? Could adding an "oil stabilizer" increase the viscosity and stop the smoking without replacing the rings? Is adding an "oil stabilizer" a bad thing for these bikes; would the extra viscosity overheat the oil because it can't flow properly; could any additives affect the interior of the engine? I'm leaning toward experimenting by thickening the oil first before I spend a chunk of change on rings and gaskets and possibly a bore job.)

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I would check cylinder leakdown before condemning the rings.  Smoke on startup is probably more likely caused by leakage past the valve stem seals, likely caused in part by worn valves and guides. 

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Don't add anything to the oil , unless you want to replace your clutch plates too. Same as above , valve seals.

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You can run 15w40 oil  or run 15w50 syn like I do.......but adding snake oil additives is a good way to screw up something like clutch plates or oil starve something you`d rather not have to replace......oil additives are a MECHANIC IN A CAN  ...where the engine should be repaired..

 

if 15w40 doesn`t help you.......rip it apart..

But I also agree with people above,,if it smokes on startup you likely have worn/defective valve seals..rings will not cause smoke only on startup..

 

B

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Yes , rings usually smoke constantly. You may have nicked a seal on the sharp corners of the groove on the valve stem where the spring keepers go.

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