Rt cylinder damage

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PhilJet09
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Rt cylinder damage

Post by PhilJet09 » Mon Aug 24, 2020 6:09 pm

Riding down a country road yesterday on my ‘16 GearUp with 8600 km. Right side started knocking really bad, so I slowed, turned around and limped home about 3 miles. Took the spark plug out and peered in the hole, saw something strange. Pulled the exhaust pipes and found this caught by the cat screens.

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Got my son’s borescope and snapped these pictures through the spark plug hole.

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Image

I guess I’ll start pulling the sidecar off.
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Re: Rt cylinder damage

Post by Mr Wazzock » Mon Aug 24, 2020 6:15 pm

Oh crap. Does rather look like top edge of piston jammed in the top of the bore and took the edge off. I did the same looking damage on a Moto Guzzi once. :( That was caused by a lubrication failure.
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Re: Rt cylinder damage

Post by Lokiboy » Mon Aug 24, 2020 6:49 pm

You can remove the right cylinder and replace the piston with the sidecar attached.

Here’s a great tip when you go to reinstall the rings.
viewtopic.php?f=25&t=53830

This thread shows the ring orientation. Now, others firmly disagree with the positioning, but for taking two extra minutes you’ll optimize the rings doing what they are designed for.

viewtopic.php?f=25&t=53945
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Re: Rt cylinder damage

Post by PhilJet09 » Mon Aug 24, 2020 8:40 pm

I got the car out of the way, it was easy, but thanks for the tip.

This isn’t great.

Image

Image
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PhilJet09
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Re: Rt cylinder damage

Post by PhilJet09 » Mon Aug 24, 2020 8:41 pm

Lokiboy wrote:
Mon Aug 24, 2020 6:49 pm
You can remove the right cylinder and replace the piston with the sidecar attached.

Here’s a great tip when you go to reinstall the rings.
viewtopic.php?f=25&t=53830

This thread shows the ring orientation. Now, others firmly disagree with the positioning, but for taking two extra minutes you’ll optimize the rings doing what they are designed for.

viewtopic.php?f=25&t=53945
That’s good advice there, thank you!
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Re: Rt cylinder damage

Post by cookiemech » Tue Aug 25, 2020 6:12 am

I've had the heads and jugs off both my (previous) 2014 Ural and several BMW airheads, so I have a pretty good feel for how everything works normally. But I'm having trouble understanding this particular failure. Mike (Mr. Wazzock) suggested that the piston jammed in the top of the bore. But how does the piston move upward enough to contact the head, unless the con rod breaks or the piston fractures? Or am I looking at this incorrectly, and pieces broke off the top of the piston, with those pieces being the mechanism of damage to the head?

Sorry to see such destruction on a fairly new model, with relatively low miles.
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Re: Rt cylinder damage

Post by Crawford Sales Co. » Tue Aug 25, 2020 7:32 am

It use to happen more on the older bikes. Something came loose inside the air filter or on the throttle body and went into the piston area and made a mess. Usually a nut or washer. You should have found it when you took the head off. By chance did you work on your bike just before you went for your ride.
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Re: Rt cylinder damage

Post by cookiemech » Tue Aug 25, 2020 8:32 am

Crawford Sales Co. wrote:
Tue Aug 25, 2020 7:32 am
Something came loose inside the air filter or on the throttle body and went into the piston area and made a mess. Usually a nut or washer.
Thank you! Makes perfect sense.
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Re: Rt cylinder damage

Post by jeffsaline » Tue Aug 25, 2020 8:59 am

Can't really see much on my computer but I'm wondering if that isn't from detonation from a low octane fuel.

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Re: Rt cylinder damage

Post by Msblu79 » Tue Aug 25, 2020 9:29 am

That is classic textbook detonation damage. What kind of fuel are you using? I see this to often in our shop. Hopefully you caught it before the crank was damaged. :(
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Re: Rt cylinder damage

Post by Snakeoil » Tue Aug 25, 2020 2:21 pm

I dunno, detonation normally creates a lot of pitting on the piston dome like somebody went at it with an ice pick. The damage to that piston and the mating cumbustion chamber looks very mechanical to me.

The initial photo showing the debris shows a piece with a rounded end. Looks like some type of flat spring. I tend to agree with Terry that you swallowed something in that jug.

Touch a magnet to that debris. If it is steel, it sure did not come from the piston or the head unless a ring broke and somehow got above the top land. But I truly doubt that is possible without more damage to the land.
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Re: Rt cylinder damage

Post by Msblu79 » Tue Aug 25, 2020 3:04 pm

Whatever you want to believe folks, I work in an engine repair shop and have seen this a thousand times. It is by far the most common failure mode for engines these days and a battle the manufacturers deal with constantly to prevent. If it were mechanical there would be marks all over that piston, the fact that is in the outer edges only is clear evidence of detonation.
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Re: Rt cylinder damage

Post by Manscout » Tue Aug 25, 2020 4:08 pm

I am going to agree with you. This reminded me immediately of Tomcatfixer's piston on the Mobile Chernobyl. His was caused from predet. damage on low octane fuel if I recall.
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Re: Rt cylinder damage

Post by Snakeoil » Tue Aug 25, 2020 7:24 pm

Msblu79 wrote:
Tue Aug 25, 2020 3:04 pm
Whatever you want to believe folks, I work in an engine repair shop and have seen this a thousand times. It is by far the most common failure mode for engines these days and a battle the manufacturers deal with constantly to prevent. If it were mechanical there would be marks all over that piston, the fact that is in the outer edges only is clear evidence of detonation.
Okay, not arguing here. But when I look at the deep v-shaped gouge in the piston near the land, I have to wonder what would cause that if not a foreign object. I understand that the land is the weakest part of the top of the piston and that detonation will break the lands. I would also expect it to flame cut the lands. Of all the damage I see on that piston, I see no indication of extreme temperature. I've never seen a piston fail from detonation that did not exhibit some form of temperature damage, be it pitting, flame cutting, scorching, etc.. Now it may be in those photos. I do see what looks like tiny particles of aluminum, ie. metal spray. But that could also just be particles from mechanical beating and chewing if a piece of steel got in there.

Google "piston damage from detonation" and look at the photos. I did because I'm certainly no expert on the subject. And I could not find a single photo where there was mechanical damage as shown above and no signs of overtemp.

Again, not arguing here. This is a learning process. But if the swirl from the intake charge took some small pieces and threw them to the outer edge of the piston, the first blow would have broken the land or at least damaged it and could have caused the piece to get stuck between the piston and the bore. And we see evidence of that. When it came free, it might have simply spit out the exhaust valve.

Tell me what you see in those photos that demonstrates detonation. I truly want to learn from this. If you can have the extreme temps that cause detonation and break a land without scorching or flame cutting a piston, I want to know that.
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Re: Rt cylinder damage

Post by PhilJet09 » Tue Aug 25, 2020 8:25 pm

I normally make it a habit to not disagree with Terry, but this isn’t from something being ingested into this cylinder. I’ve developed good work practices from years of being an A&P/IA that prevent me from being sloppy enough to leave hardware in dangerous places. Plus, it’s been several thousand miles since I’ve been inside the air box, and have never had a reason to take apart anything downstream from there. Just for giggles, tonight I opened the air box and the filter was still there, tightly sealed, nothing out of place. I also took the factory clamps off the throttle body to have a look around. Butterfly was still there, no hardware missing.

Looking at the impact damage on the piston, it’s pretty clear that it’s from pieces of the upper ring, looking at the shapes.

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In this last picture, you can see porosity in the aluminum. Interesting.

Image

Of course, I don’t know for sure what caused this. Did the aluminum fail and allow part of the ring to break out? Did the ring break, then cause this?

Here’s more background on this bike. Initially, I could kick start this thing, hot or cold, no problem...usually on the first kick. About 4000km ago, riding home, came to a long light, idle got slower and slower, until it finally died and didn’t restart very easily with the starter (line of traffic behind me). Got home, drained and flushed the fuel system since I had just filled up that morning, new fuel (always top tier 93 octane), new plugs, and hooked up to the new-to-me OBDwiz and and adjusted the TBS, including turning the idle up a bit. Ran fine, but still not as easy to kick start as it used to be when cold. It’s been like that until a couple weeks ago, something changed again. Very difficult to kick start, don’t even try anymore, runs ok, but idle seems slower. I figured the cables were still stretching, so I turned it up a bit, changed the plugs (exterior of the old ones were rusty, I hate that), checked the valve lash, no adjustment needed, and did another TBS, also changed all the fluids again, including the brake fluid since my rear brake switch stopped working and I had to install a new one...might as well change the fluid in all 3 systems while I have the EZvac out. That brings us to current.
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