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oil level after shutoff/smoking idle

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hey gang!

 

 

i'm in the midst of a smoking idle issue on my xl600r. its probably burning oil but i haven't quite diagnosed it yet. its probably the rings-although the bike still has compression. i'm thinking the oil scraper rings are giving up the ghost. 

 

however the bike only seems to smoke lightly at idle and not when revving so i'm not too concerned yet. however i would like to make absolutely sure my oil level is correct in the meantime. after running the bike for 5 minutes or so i shut it off and check the oil. oil level is a teeny bit over the 'full' mark. i check it a minute later, its a bit lower, another minute, lower. after about 10 minutes the oil level is below the dipstick. now i know the oil check valve thing doesn't really work brilliantly and allows oil to drain back into the crankcase. i'm a little concerned that mine seems to drain as quickly as it does.

 

now all this being said, which oil level should i believe? the level that is read almost immediately after shutoff? (after all the bubbles and stuff have gone away) or the level that happens say 10 minutes later? i've definitely overfilled the bike before - it shot oil out the crankcase breather like crazy - and i don't want to do that again, but i also don't wanna run this thing too low on oil either. 

 

on the topic of the smoking? i rebuilt the motor myself less than 1000 miles ago. i replaced the valve steam seals and it doesnt smoke on startup, so i don't think those are the cause. i did not replace the rings, they seemed to be okay and the cylinder looked immaculate, maybe that was a mistake on my part. i'm sorta hoping that i have an issue with my idle circuit which is leading to the smoking, however the idle jet is clean and clear. i'll be playing with the mixture screw and spark plug, but i'm starting to think all signs are pointing to the rings. the bummer is i know there is an aftermarket piston in there and i forgot to write down the name of it so i wouldn't even be able to order the rings online until i had the whole dumb thing taken apart! bah!

 

 

 

any thoughts gang? its an 87 xl600r that runs on e85 hahha!:goofy:

1K9A3473.jpg

Edited by patrickarter

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Check the oil immediately after shut down. You can't just slap new rings in it , even if you knew what piston you have. The cylinder needs to be measured correctly for wear and roundness , THEN you determine what rings and piston will fit , after honing or boring as needed.

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NO. If your rings are done , then the cylinder needs attention too , which means piston replacement also.

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13 hours ago, patrickarter said:

 



 

 

 

 

 

1K9A3473.jpg

Nice pic!

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Definitely possible to replace rings only.

Measure piston, measure cylinder. If the clearance between the two, and the OOR are acceptable, a ball hone and rings could solve your problem. 

However, you might check/replace the valve stem seals first. Idle means high vacuum which will suck standing oil from crackly or worn intake valve stem seals. Not a lot of oil pools on the valve stems but idle is the easiest time you'll notice symptoms of valve stem seal leakage.  Also likely to give a noticeable puff after no throttle mid/high rpm decel when you open the throttle again. Less vacuum as the carbs are opened so not as likely to suck oil. 

An easy way to check valve stem seals is to remove the header and apply vacuum to the exhaust ports. If they are leaking, you'll get some oil running down the stems. Same for intake side but it's harder to see, as the intake valves dont dry out as much as the exhaust. 

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I actually replaced the valve stem seals when I rebuilt the motor a couple months ago, I'd assume it wasn't that. I suppose I could run that test as well.

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On 5/7/2017 at 2:27 AM, patrickarter said:

 

 

 

 

 

 

on the topic of the smoking? i rebuilt the motor myself less than 1000 miles ago. i replaced the valve steam seals and it doesnt smoke on startup, so i don't think those are the cause. i did not replace the rings, they seemed to be okay and the cylinder looked immaculate, maybe that was a mistake on my part.

 

 

 

How did you determine rings "seemed to be OK"?

If it were me at this point, I'd try a compression test, & then do a second compression test by adding/squirt a little oil thru spark plug hole into cylinder, and see if compression comes up. If compression did increase, rings are culprit.

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