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Old 18-Sep-2009, 12:14 AM
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Ian 748 Ian 748 is offline
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Another oil in airbox question

An old favourite I know butÖthis much oil in the airbox is not good right?? I cleaned and dried it out then took it for a easy ride to get an idea how much oil is being blown up. Pic is after only 145 easy-ish miles.
Compression check shows ok, cylinder leak test shows ok, not burning oil, no puff of smoke on start up and it pulls better than ever. Itís not been over filled and started doing this quite suddenly. Anyone had the same to this degree or got a notion what might be going on.
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Old 18-Sep-2009, 12:46 AM
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Your system has a one-way valve that allows outward flow only, and a oil separator that acts like a maze for any entrained oil droplets that try to leave the crankcase. This (normally) small amount of oil then drains back into the crankcase instead of entering the engine intake.

On Ducati street bikes the one-way reed valve is located at the engine case opening. During certain conditions of high engine rpm and light load, more oil is entrained so the reed valves’ small drain holes have difficulty returning the additional oil to the sump quick enough. The oil separator can fill with oil and get sucked into the intake tract. Higher compression engines or worn piston rings have more blow-by, so the likelihood of oil being puked into the airbox is greater.

So it's possible that the drain holes are partially plugged and can't keep up.

One way around this problem is by hollowing-out the reed valve to remove the constriction on drainage. Alternatively, STM valveless breather connector can be used.

Then use a one-way reed valve at the airbox connection. A 748RS remote breather valve works well here, see below.

Photo by DukeDesmo
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Old 18-Sep-2009, 01:35 AM
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Quote:
Originally Posted by Shazaam!
Then use a one-way reed valve at the airbox connection. A 748RS remote breather valve works well here, see below.

Photo by DukeDesmo

I have one just like that on my 998R
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Old 19-Sep-2009, 11:34 PM
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Ian 748 Ian 748 is offline
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Quote:
Originally Posted by Shazaam!
worn piston rings have more blow-by, so the likelihood of oil being puked into the airbox is greater.

One way around this problem is by hollowing-out the reed valve to remove the constriction on drainage. Alternatively, STM valveless breather connector can be used.

Then use a one-way reed valve at the airbox connection.
Thanks for that Shazaam. Sounds logical I guess that even though comp test was ok itís not as good as it once was, blow by will have increased and the drain holes arenít coping for sure. If Iím going to try a new valve type I may as well perform some surgery on this one and see how it goes.
Cheers Ian.
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Old 19-Sep-2009, 11:39 PM
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Quote:
Originally Posted by skidlids
I have one just like that on my 998R
And is your box clean and dry or oily and orid ?
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