scratched cylinder wall

[JJH]

1979 R65 so the steel lined cylinder.

I am in the process of replacing my pushrod tube seals.  I now have the head, cylinder, and piston removed.  I cleaned the carbon off the head and piston.  I started to look at the cylinder and noticed I have three vertical scratches.  The three scratches are about 5 cm apart from each other, and travel maybe 25 cm.  You can see them with your eye.  You can barely feel them with your finger , but they will "catch" a finger nail.  They are deeper (easier to feel) at the top, and gradually go to nothing.  Not really experienced with this.  Looking for advise on the next step. 
Thanks,
 John   

[Justin B.]

Other than leaks was it using/burning any oil?  If not I'd be inclined to let "sleeping dogs lie", but I'm a cheap SOB or so I've been told.

[Adrian]

The three scratches are about 5 cm apart from each other, and travel maybe 25 cm.  You can see them with your eye.  You can barely feel them with your finger , but they will "catch" a finger nail.  They are deeper (easier to feel) at the top, and gradually go to nothing.

,
Hi there - I have some small damage in my 1984 barrels - both of them have a couple of "nicks" in tem - about half way down - they are tiny areas that are easily seen and can be felt - as it someone has taken a small piece of the nickasil out of the wall.
.
The barrels have been like this since I bought the bike in 1992 and have never given me any problems .
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If the scratches are not causing any oil smoke or the oil consumption is not high (1 liter per 1000 miles is apparently acceptable) then it probably is okay to ignore it.

[Barry]

I wouldn't worry about them. Even with perfect bores there is always some leakage past the piston rings and the tiny amount added by a few fines scratches won't make much difference.

[JJH]

To answer questions, the pushrod seals were leaking quite badly, if the engine was burning oil, I don't think I would detect this.  I did not see white smoke from the exhaust when I rode.  Now can I just reuse the rings or do I have to hone and buy new rings?

[Barry]

Now can I just reuse the rings or do I have to hone and buy new rings?
                   

The ideal scenario would have been to make that decision on the basis of a compression or leak down test but you could re-use them if the miles on the engine are not too high.

[mrclubike]

They are not that expensive from MOTOBINS
If they are not oversize
I would change them

The exchange rate is really low and if you order them today you would have them by next Tues or Weds
But you really need to measure the bore to tell if the bore is worn out  or is already bored over sized

[nhmaf]

+1 on installing new rings if you've had the piston out and the rings have more than a couple thousand on them.  They don't cost much, and it may be that the scratches are from one of them "sticking".  Just be certain to thoroughly clean the ring grooves first.

[Matt Chapter]

+1 on installing new rings if you've had the piston out and the rings have more than a couple thousand on them.

Where were you when I did my pushrod seals last year!?  I'm really regretting not replacing the rings at the time.

[Tony Smith]

I'd like to see a photo of the scratch(s), I'd also like to know what caused them.


A mark that can catch your finger nail is significant in the grand scheme of things , certainly enough to also catch the end of a ring for example.

I remember reading years and years ago how good a job rings, and in particular oil control rings do. Apparently a six cylinder engine using burning exactly 1 drop of oil per piston stroke will consume its entire reserve of oil in a couple of miles. Sobering when you think about it.

[JJH]

Here are some images.  Interpreting images from a reflective surface can sometimes be difficult.  Please ask questions if addition information is required.

As for what caused the scratches, I have contacted a medium but she told me she can't read cylinders

Thanks for all the help

[donbmw]

Looks like normal wear that I have seen on other cylinders from motorcycles, watercraft and aircraft cylinders.

[Tony Smith]

Looks like normal wear that I have seen on other cylinders from motorcycles, watercraft and aircraft cylinders.

I would suggest that there is no normal wear that could cause those marks. It is not unusual to see such damage, but it is the result of an abnormal event.

Something has got in there  - either by way of a compromised air filtration system or because something came loose in the combustion chamber.


let's leave the air side of things because I am sure that as part of your rebuild you will be looking at filters and trunking anyway.

Leaving something loose in the combustion chamber - the usual suspects are the insulation in the spark plug falling apart or bit of carbon coming loose and rattling around the chamber.

I would probably re-use that cylinder and cross my fingers - with good prospects that all will be fine.  But I'd be keeping an eye out on eBay and the like for a pair of serviceable later model barrels.

[Bob_Roller]

What do the piston rings look like that were in that cylinder ??

[JJH]

They looked fine to me, but I must admit that they are the first rings I have ever looked at.  There is no obvious break or cut or piece missing.