what causes this cylinder wall polishing

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Hello,

see attached picture.

What is causing this area of the cylinder to look polished with no cross-hatch remaining visible? Is it lubrication related or mechanical, metallurgy?
How comes it's isolated to that area? It's only on this visible side, the opposite site is normal.

Is there any possible way to prevent this? Using an oil with high zinc, motorcycle oil with moly or boron? Wolfram additive?

Engine in question is a 805cc liquid cooled V-Twin



vlcyl_polished.jpg
 
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I know that running certain engines at consistently low rpm can cause egging of the cylinder. Could be a possibility but not sure here.
 
I think it has to do with how it was honed. A singe fine hone would probably polish like this. Plateau honing is done on some engines. Honed coarse and deeper, then honed again with a finer hone to knock down the peaks. If i understand it right, the plateau hone holds more oil on the cylinder wall and wears less.
 
What's the piston skirt wear look like? Probably wear from piston skirt rocking ... maybe the skirt to cylinder clearance was too large.

How many miles are on this engine?
 
How is the motor mounted related to the photo … ie, is that the low side of a vertical shaft or what ?
 
Seen that many times on a highly used engine. The piston skirt likely has some wear as well. Eventually the cylinder becomed egg shaped. The ones I encountered were engines that ran at a constant RPM without much variation in operating RPM's.
 
That looks like a relatively normal wear rate. It's good to keep in mind that there may not be a single contributing factor to the rate of wear or the uneven wear.

I don't know if you are trying to fix a problem or extend engine life. But my very first guess is piston pin offset (or the associated cylinder bore offset/lack of offset) is a contributing factor.

If the engine has provided a good service life, why not simply repair it with equivalent parts and expect a similar lifespan? If the engine failed early, are there quality aftermarket/race parts that would solve the problem.

With many modern engines, engineers have been able to use incredibly short skirt pistons, while simultaneously achieving superb wear rates. This is done partly via pin and cylinder offset, along with weight reduction and very high quality rings.
 
thanks for your input,

the engine in question is a Suzuki V-Twin, never been opened before. Engine has 16000 miles on it.

It comes out of a M50, I was thinking of buying that engine as a replacement when my C50 engine goes out.

Cujet said it looks like a relatively normal wear rate - but at 16000 miles only?

Piston has minimal polishing marks.
 
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Below is a copy and paste for glazing of cylinder bores...

Glazing of cylinder walls typically occurs during engine break-in and is caused by improper operation during the break-in period by operating at power settings too low to allow the piston rings to seat properly with the cylinder walls.
 
Quote
Glazing of cylinder walls typically occurs during engine break-in and is caused by improper operation during the break-in period by operating at power settings too low to allow the piston rings to seat properly with the cylinder walls.


I've rebuilt a lot of motorcycle engines including some of the same engines several times over the years and I'm going to agree on the likelihood of this, given the info you've provided so far.

It would be interesting to measure the piston to cylinder wall clearance and the ring gap. As low of mileage as this one is you might be able to save yourself a bunch of time and trouble. If the piston to cylinder wall clearance is still within service wear limits and the pistons look OK you might get away with honing a cross hatch and new rings, just be sure to check the ring gap in place prior to assembly and stagger the gaps properly upon reassembly. I don't know your particular bike at all, but there should be a published spec for cylinder bore and service wear limits. Older bikes you could use a feeler gauge, some modern bikes you can't do this because of the piston shape, there is a bore spec for that piston and that's it. If you don't have the tools any good machine shop would probably check it for a couple of bucks.

I have had excellent results from Flex-Hone (looks like a bunch of abrasive nodules on a wire brush), the quality of finish and oil retention is excellent, and the stock removal is almost nil. No special tools required, a cordless drill works fine. After honing DO NOT use solvent of any kind, wipe the cylinder walls with a clean rag saturated with clean oil until the rag comes out clean. If you wash the cylinder with solvent after honing you will be right back where you started but worse. The solvent carries the abrasive particles into the pores of the metal and it will result in accelerated wear and maybe even glazed rings.

The reason why I am agreeing with 1978elcamino is I've seen this before for the reasons described. On a new build the ring edges are sharp and the fine structure of the cylinder walls if properly honed are "open" for lack of a better word. It's an abrasive situation even if the walls were oiled properly on assembly. The first start should be only a couple of seconds and shut the engine off immediately. The edges of the rings will have turned very, very hot. Wait a few minutes, start the engine, do not tach it up, run for 30 seconds, shut it off, wait a few minutes. Now start the engine and ride the bike for a few miles and just ride normally, don't beat it, don't baby it. Let it cool off, then go for a 50 mile ride, come home, change the oil. I have no idea how many bikes I've done this with and never had a problem.

If moly-faced rings are an option for that bike you might have better results from that as well..
 
wow, thank you so much CCI!

I just googled about the flex-hone, never seen that before. I even have a local merchant.

Now, there are different materials available for the flex-hone, "normal" to different carbides - which one would I choose?

thanks
 
Did you, or are you, going to measure the cylinder diameter, roundness and taper to see if it's out of spec?
 
Choice of hone depends upon composition of cylinder walls -- I don't know anything about the specifics of your engine, but there may be some tech guidance available either in the factory service manual, from a local shop with a good reputation for rebuilds, or maybe a dealership. What year, make, and model bike are you working on?

And as ZeeOSix is pointing out, measuring for diameter, roundness, and taper is essential.

If you post some photos of the piston piston skirts (thrust face fore and aft) there might be more that could be determined.
 
Reading back through the thread I think I understand this is an 805 cc Suzuki V-Twin engine, so what follows is not advice, it's just how I would think about it based upon my own experience. You should check with someone local who knows these engines, maybe even get a factory service manual.

It doesn't look like your cylinders are plated, so I would imagine a 320 grit silicon carbide hone would work. Brush Research makes a hone specifically for this size. Just make sure the cylinders are not plated, if they are, then you need to use a different abrasive type.

The important part is to use the same oil as you run in the engine, get a fair amount of it spread on the cylinder wall, then get a stroking pattern that runs the brush evenly top to bottom, run the brush through so it just goes out either end of the cylinder a bit, stroke speed and rpm are whatever gives you a good 45 degree angle on the cross-hatch. It's experience, there is no way to describe it exactly but this is a good reference:

https://blog.brushresearch.com/flex-hone-tips-cylinder-walls-and-cross-hatch-angles

Here's a little more info of a general nature:

https://www.hastingspistonrings.com/tech-tips-faqs/cylinder-bore-refinishing

Once you have established a good cross hatch there is no reason to keep going. Now wipe out the cylinder with a clean white rag soaked in the same oil, keep going until the rag comes out clean. Then wash the cylinder in hot soapy water, dry immediately, and oil it again.

Do not use solvent of any kind, this will wash abrasive into the pores of the cylinder wall and it will damage the motor.

One of the great things about a flex hone is if you use it right it will take care of any sharp edges including at the cylinder base, the rings go in much easier with less damage.

The most important part though is to measure the cylinders and make sure the piston to wall clearance is still in spec. If the pistons are cam-ground you may have a difficult to almost impossible time measuring the piston skirt accurately, it's worth checking the factory service manual or with a local dealership to get an exact bore size. There should be a service wear limit published, if you are inside the limit and the pistons look good then this should work.

Also pay careful attention to how you stagger the ring gaps and how you install the wristpin keepers. I see more problems from that than everything else put together.
 
Originally Posted by ZeeOSix
Did you, or are you, going to measure the cylinder diameter, roundness and taper to see if it's out of spec?


Important! With out calipers or gauge's, you can use a new piston ring and measure the gap at several points of piston travel. Use the piston to square it in the bore. Then measure the gap and see if it's with it in spec. If the gaps are too wide, the bore will need to be bored to the next oversize.
 
Originally Posted by spasm3
Originally Posted by ZeeOSix
Did you, or are you, going to measure the cylinder diameter, roundness and taper to see if it's out of spec?


Important! With out calipers or gauge's, you can use a new piston ring and measure the gap at several points of piston travel. Use the piston to square it in the bore. Then measure the gap and see if it's with it in spec. If the gaps are too wide, the bore will need to be bored to the next oversize.


Yes -- this is a good trick, and brings up another good point. Flex hones do not resize the cylinder, and they will not correct an out-of-round condition. It is possible for cylinder walls to go out of true in a surprising number of directions, especially if a connecting rod is bent or twisted. That's unlikely on your bike but worth mentioning.

If you do as spasm3 is describing, you can check the ring gap with a feeler gauge a few inches up from the bottom, at the middle, and at the top just below where the rings stop in the normal stroke, and then just above where the rings stop to see if there is a "ridge." As was pointed out, the ring has to be perfectly square in the bore, the top of the piston will work if it is clean.

There will be a published spec for the ring gap. If the ring gap is within spec, that's the good first step, now make sure that the ring gap doesn't vary through the range of piston travel. If the ring gap is consistent throughout the stroke and within spec, I imagine you's be OK.
 
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