Methodology for diagnosing motor issue - 749 - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 22 (permalink) Old May 4th, 2019, 6:34 pm Thread Starter
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Methodology for diagnosing motor issue - 749

Since I got the bike, I'm starting a new thread off of my questioning if rebuilding the xx9 motors are economical.

Short story - Original owner suspected over-rev going into a turn back in 2015, motor started "pinging" or "knocking". Pulled over and hasn't been ran or looked at since.

I'm starting with draining the oil into a clean pan, inspecting the screen, and cracking the oil filter open, but beyond that this is a little new to me.

Should I be hesitant to crank it over with the plugs removed to listen for anything in particular? There's no way to easily look at the bottom end is there?

Thanks
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post #2 of 22 (permalink) Old May 4th, 2019, 6:52 pm
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One thing Iíve learned over the years is to never trust someoneís else diagnosis or even symptom description. The Ďknocking or pingingí previous owner heard might just be a battered clutch basket or something silly.

That being said, did you find any shavings or debris in the oil, filter or screen? If not, dump clean oil into it and fire it up. If itís already knocking itís probably not going to die running at idle for 20secinds for you to hear it yourself.

To answer your question about checking the bottom end; thereís no easy way to check as the cases are split vertically. However, Iíve had some luck removing the spark plugs, putting a piston near TDC and pushing on it with a punch. Sometimes if a rod bearings spun, the piston will give way a little under your hand pressure without the crank spinning. Thatís a pretty clear indication the bottom end needs disassembly.

To check crank bearings you can use a crank turning tool to manually turn it without spark lugs and feel for Ďgrittinessí or debris in the roller bearings that way.


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post #3 of 22 (permalink) Old May 4th, 2019, 6:53 pm
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You canít really see much with an inspection camera , Iíve tried. Drain the oil , check the screen. You could cut the filter open. The second thing would be examine the plugs. Third, do a compression check. Rotate the engine by hand with the plugs out, you might be able to feel something. If you can find an inspection camera with a small enough head on it you could check the cylinders and valves. Pop the valve covers and rotate the motor, you might see a bent valve or valve train issue. The first thing I always think on an over rev is valve or piston damage.

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post #4 of 22 (permalink) Old May 5th, 2019, 2:44 am
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comp test, leakdown, turning it over, if it runs without noises that make your skin crawl, give it an oil pressure test. if it has rooted big ends it'll have 40 - 50 psi oil pressure rapping wildly.

otherwise, pull it out and you keep pulling it apart until you find something wrong.

i had a 748r in once that had previously been diagnosed with a terminal bottom end failure due to the noise it was making. turned out an opening shim had come out. no idea how, but that's what it was. just follow the clues.

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post #5 of 22 (permalink) Old May 5th, 2019, 6:52 am Thread Starter
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Thanks everyone for the great information. Here is where I am after draining the oil:

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post #6 of 22 (permalink) Old May 5th, 2019, 7:03 am
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That canít be good. Time for the experts to step in. Warm up the wrenches.

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post #7 of 22 (permalink) Old May 5th, 2019, 7:18 am
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Definitely doesnít appear to be bearing material on the plug. Iíve seen plugs look similar before with no ill effects. Iíd pour oil in it and start it to listen for yourself.


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post #8 of 22 (permalink) Old May 5th, 2019, 11:57 am Thread Starter
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Unfortunately getting it to fire up might be delayed -fuel pump flange o-ring is no bueno after draining the last of the old gas. The shavings on the screen are somewhat worrisome as there is some copper in there. I'll continue to go through it bit by bit. Waiting on a thin-wall socket to get the plugs out and start turning it over. That will be today, so I might be posting more here.

Are the valve cover gaskets\seals re-usable?

Again, all of the dialogue is really appreciated!

P.S.
Anyone recognize this clutch:
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post #9 of 22 (permalink) Old May 5th, 2019, 5:12 pm Thread Starter
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Well it's time to spin the motor with fire. Hand rotating (using the rear wheel) with the plugs out doesn't seem to be an issue. Plugs look fine. No noises or strange play in the drive train. Valve train area looks good and timing is correct. Pushed against pistons with a long t-handle allen wrench at TDC +/- and couldn't detect any slop.
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post #10 of 22 (permalink) Old May 7th, 2019, 8:02 am Thread Starter
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Some video\audio of the motor turning over using the starter with and without plugs\clutch pack

no plugs:

plugs\no clutch:
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