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Oil Burning

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Once in a while, when I start my 1984 XL 600R, it will burn oil. It does not do this all the time, just once in a while. Otherwise, when she is running, there is no smoke at all. What would cause this?

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Bad valve stem seals will allow oil to leak down the valve stems after the engine is shut off. The oil burns off when the engine is started and usually manifests itself as blue smoke mainly on startup. Usually it's not something to worry about unless you notice a lot of oil consumption between changes.

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Possibly just some old valve seals. Until you're getting paid by the city for pest control, I would'nt worry about it.

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Ya know, when I hear someone say something about thier machine smoking, I reflect back to my youger days, when we had very little money and if it ran, but smoked like a chimney, we just ran the cheapest oil we could. I've seen whole summers of fun run on bar and chain oil.:)

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The thing is, it does not do it all the time. I'd say out of the last 50 start ups, it did it twice. All the other times, it did not smoke at all. I am wondering if it has to do with the decompression valve sticking open. Any thoughts?

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we just ran the cheapest oil we could. I've seen whole summers of fun run on bar and chain oil.:D

:) lol times have changed (and I got ripped). I just had to go buy a quart of Bar&Chain oil for my saw this morning and it was $7.39 for a quart!!!

Should have gone to home depot but I like to support the little hardware store here in town when I can...ohh well.

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The thing is, it does not do it all the time. I'd say out of the last 50 start ups, it did it twice. All the other times, it did not smoke at all. I am wondering if it has to do with the decompression valve sticking open. Any thoughts?

Well, I'm not familiar with the crankcase venting system on you bike, but if it feeds back into the intake system, a little oil may find its way into a bend or pocket of something, and/or the film could drain into a puddle after the bike is shut off, and when you stand it up and start it the miniscule puddle of oil is sucked into the engine. The harder you ride it before its parked with have more efect on this. Also if it is just worn valve stems/guides combined with old seals, if severly worn it would smoke all the time, but could be just enough so that if the engine stops in just the rite place,and sets, a little oil will get by. Are you shure its oil? if the choke is on, it could be fuel. Are you shure its not just condensation? Are you its a motorcycle?:) If the de crump preston valve[lever] was staying engauged it should'nt start/run well at all[coughing and hacking]. Check it if ya feel the need, I'd check adjustment on anything I thought might be the cuplrit, its far less expensive than ride until something breaks and going:prof: I found the probloom. It's not hard to change valve seals, and on a older bike, it may be all you need. Back to the begining, if the crankcase vent feeds back towards the air filter, take the filter out and see how much oily mess is behing it.

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It is definitely oil, but like I said, it happened twice in 50 startups, so maybe a little oil is backing up with the crankcase venting system.

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