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Discussion Starter · #1 ·
My '02 900 Sport was acquired in April of 2017 with less than 10K miles. Right now at 15K I'm getting tremendous blowby from the rings - enough to saturate the airbox and blow out the right side crankcase gasket.

The bikes history shows 5 oil changes in my 2 1/2 years of ownership including a recent switch to 0W40. An experienced Ducatisti had recommended 15W50 oil and that opinion is backed up by Ducati's manual and specifications so that's what I ran. I ride in generally temperate conditions almost entirely on back roads. There's no roasting of the engine at traffic lights and almost no stop and go traffic. I've always been careful to keep engine revs low until the oil temp gauge is at the end of the red area and at the beginning of the normal operating range. I run it fairly hard but don't shift past 8000 - 8500.

My theory that 50 weight oil has damaged the motor is based on a recent comparison of startup noises made after changing to 0W40. With the 15W50 the top end was clangy and ringing for a much longer period at cold start. With the 0W40 initial mechanical top end noise is quieter at startup and minimizes much faster. I'd estimate 150 - 200 cold starts with 50 weight over the last 2 1/2 years was enough to wear out the rings.

What I'm hoping to discover is whether there's a correlation between prematurely worn rings on air cooled two valve engines and 50 weight. Does anyone have input on this? Might save people a lot of aggravation.
 

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I ( independent Ducati mechanic as well as dealership experience) have always and plan for the future to run 20/50 oil in all ball bearing top end ducati's, this includes 600,620,650,695,750,800,900 and all desmoquattro's ( 4-valve ball bearing heads). No the 50wt did not cause a problem unless you are over filling it to such a level crank case pressure is too high.

If you are having ring seal issue something else likely has damaged/worn your cylinders or someone put it together incorrectly.
 

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Overfilled or blocked breather valve.

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My '02 900 Sport was acquired in April of 2017 with less than 10K miles. Right now at 15K I'm getting tremendous blowby from the rings - enough to saturate the airbox and blow out the right side crankcase gasket.
Broken ring? Stuck ring?

:wink2: (don't forget to subscribe to your thread!) :smile2:
 

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Blowby but no smoking ? I would check the breather valve first. Then check the plugs and do a compression check to figure out which cylinder is the culprit .
 

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Discussion Starter · #7 ·
Overfilled crankcase - no; that's what the sight glass is for. Blocked breather - no; it was examined thoroughly and has a working valve and no buildup of any kind. I'm not sure how you could have a breather that creates a highly pressurized crankcase and excessive oil on the airbox at the same time. Incorrect assembly - maybe; Ducati assembled it in either 2001 or 2002. Broken ring; maybe, it runs perfectly except for a recently acquired low idle that just preceded the copious amounts of oil in the airbox. I'll be running a wet dry compression check this week.

I'm quite sure now that loud ringing and clanging at cold start is a byproduct of insufficient lubrication and too thick oil. I'm not sure a Ducati engineer could talk me into going back to 15W50 oil after hearing the difference 0W40 makes at startup. We're talking about a bike that is kept in a temperature controlled basement so starting oil temperatures range from 65 - 75 degrees. Excessive top end noise at that temperature has to be too thick oil.
 

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Overfilled crankcase - no; that's what the sight glass is for.
which sight glass did you use? The one on the clutch cover side or the shifter side?

15W50 oil could not be the cause of worn rings. Your theory is without merit in that regard.

An oil filter with a faulty bypass valve *could* result in low oil pressure which in theory could result in worn rings and compression blow by.

Unless you are starting a bike in sub-zero temps, the 15W50 will behave like any other oil would.

Your oil change to 0W40 is probably too thin, but assuming you changed the oil filter, I would counter argue the filter is the more likely culprit than the oil.....sean
 
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Overfilled crankcase - no; that's what the sight glass is for. Blocked breather - no; it was examined thoroughly and has a working valve and no buildup of any kind. I'm not sure how you could have a breather that creates a highly pressurized crankcase and excessive oil on the airbox at the same time. Incorrect assembly - maybe; Ducati assembled it in either 2001 or 2002. Broken ring; maybe, it runs perfectly except for a recently acquired low idle that just preceded the copious amounts of oil in the airbox. I'll be running a wet dry compression check this week.

I'm quite sure now that loud ringing and clanging at cold start is a byproduct of insufficient lubrication and too thick oil. I'm not sure a Ducati engineer could talk me into going back to 15W50 oil after hearing the difference 0W40 makes at startup. We're talking about a bike that is kept in a temperature controlled basement so starting oil temperatures range from 65 - 75 degrees. Excessive top end noise at that temperature has to be too thick oil.
It's the pressure in the crankcase that is forcing the oil into your airbox, unless you're doing massive wheelies i'm guessing you have a broken ring, but a compression test will confirm it.

15w-50 is not 50 weight oil, there's a huge difference between them, and there's nothing wrong with running 15w-50 in an air cooled engine, it's certainly not too "thick".

The ringing and clanging at cold start sounds like the start of a starter sprag issue, as the sprag wears they develop back lash because the tolerances open up and as you try to start it the varying load due to the rotation of the pistons in the bores causes backlash and creates that noise.

I agree with Iwannaduc and am curious which sights glass you're looking at, sure sounds like it could be over full.
 

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My experience was that I ran 10W/50 or 15W/50 in my 1993 M900 Monster almost all the time. After I moved to NH, I would switch to 10W/40 for the ends of the riding season (April/May, and Nov/Dec), when it was kept in an unheated garage, and started and ridden at temperatures around 20F to 30F (-7C to -1C) on a daily basis.

It ran well with those oil weights, and did not wear the rings, or anything else, prematurely. I replaced the original piston rings at 122K miles. I was about to replace them again at 265K miles, but we got taken out by a hit-and run driver first (in 2017). The bearings and bottom end, and transmission, had not been opened since it was built.

0W/40 I would not advise. Remember that the transmission also uses the same oil supply.

PhilB
 
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Also know that air cooled cylinders will transmit quite a bit of noise when cold if the rubber pucks between the cylinder fins fall out. The noise has always been there perhaps but the pucks are now old and hard so falling out. Just a possibility for start up noise, once warm the piston to cylinder is tighter so less noise.

You might do a leakdown test as well to ring seal on each cylinder. If you come up under 20% cold leakdown it will be less likely rings. Rings often do not fail on their own so it will be more likely a glazed/scored cylinders
 

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Also know that air cooled cylinders will transmit quite a bit of noise when cold if the rubber pucks between the cylinder fins fall out.
Man, that's no shit! Back when my dad and I used to go on long desert rides on 1970s dirt bikes (air cooled) we'd leave at first light during the winter in Tucson. In the 70s Tucson was experiencing some record low temps ... them ring dings would be bangin' and clangin' until the engines got good and saturated with heat. Sounded like shakin' a bucket o' nuts!
 

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The most common cause of prematurely worn rings is dust in the intake. The other possibility is it's glazed up the cylinders. I would check the air intakes looking for anywhere dust could get in like split hoses, boots, etc.
Glazing on the other hand is usually caused be excessive idling.
Finally it might also be worth checking for fuel dilution type issues like running excessively rich, leaking carb needle and seat etc.
I agree with a previous post, do a compression test first so you know for sure it is worn rings.
 

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Yep, forgot that it uses a nikasil treated cylinder so ignore that part.
 

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I also thought that dirt making it past the filter and into the cylinders might be another cause, at least it is much more likely than 15w50 causing a problem. Compression/leakdown test is what is needed.
 
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