Crankcase Blowback - Kawasaki KLR 650 Forum
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post #1 of 5 Old 07-24-2019, 01:06 PM Thread Starter
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Crankcase Blowback

Is blowback from the crankcase a useful measure of oil consumption on a KLR? I've always removed the oil cap on an idling engine for various cars & bikes to check this. I haven't seen it mentioned for a KLR650 and I'm wondering why not?
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post #2 of 5 Old 07-24-2019, 03:23 PM
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It's a thumper. When you open the oil cap about 650cc of air will come out. Well, perhaps only 600cc, as the other 50cc will be oil.

In a more serious vein, the engine does have a crankcase breather that is a tube extending from the crankcase to the airbox. It does a pretty good job of breathing back and forth. If you remove the oil cap that breather becomes the path of most resistance, the oil fill hole the path of least resistance. Lots of stuff will come out. That fact is not an indicator of the health of the engine.

Don't worry, someday you'll change the oil, forget to put the cap back on, and start it up. You'll see firsthand...
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post #3 of 5 Old 07-24-2019, 04:23 PM Thread Starter
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Thanks, I figured there must be a reason I hadn't seen mention of it.
Does that mean an oil burner is going to leave some residue in the airbox?
Perhaps I'll just look at overall condition & maintenance and buy a case of oil.
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post #4 of 5 Old 07-24-2019, 07:20 PM
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My experience is limited but, aside from looking at the top of the piston, oil burners provide surprisingly little evidence. My experience is that 100% of '08 and '09 are oil burners. Others have exactly the opposite experience. Suffice it to say that enough of the '08 and '09 burn oil that they are infamous for it.

All KLRs will burn oil when running for extended periods at more than 5000rpm. There's a fix for that, should you become interested in it.

"They are a curious affair", Tom said royally.

Tom [email protected]

“She went out slowly. The way she did it hadn’t been learned at business college.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte


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post #5 of 5 Old 07-24-2019, 07:33 PM
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Even when my 1987 was burning 1 pint per 400 miles, there never was any oil misting into the clean side of the air filter box. And the exhaust was devoid of smoke according to following riders.

I will therefore suggest that modern 4 stroke engine oils have been re-formulated to appease the Green Environmentalism types.
(What they don't see won't hurt them.)

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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