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TOPIC: Aftermarket piston rings

Aftermarket piston rings 7 months 3 weeks ago #21623

  • StanG
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I had some beautifully looking rings but the point is you need new ones so they seal the new deglazed cylinders. My take on this is the old ones are out of shape, which was altered to fit the old block during brake in period and afterwards. Plus, they went through countless cycles of heating and cooling, so not as 'fresh' and easy to work with the groves on the cylinder sleeve surface as new. That makes them less flexible to create a good seal in new environment. But of course, they would work to a degree if nothing else available, and I bet had been done in war and remote places with success.
In case of these, not having a distinct chrome top ring makes me a bit worried.

I wonder what's Kawboy's take is on this.
1982 Kawasaki KZ1300 A4
>>> Need a 79 - 82 frame with title.

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Aftermarket piston rings 7 months 3 weeks ago #21625

  • Kawboy
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I wonder what's Kawboy's take is on this.
You asked, I tell all (that I know)
We are dealing with cast steel liners and cast iron piston rings. The rings are slightly softer than the cast steel liners and will "reshape" themselves to fit the liners but the liners will also "reshape" themselves to a lesser extent than the piston rings. In the end you get a somewhat round bore with somewhat round set of piston rings. The worst thing that could happen is you pull the cylinder off of the pistons for whatever reason and then reinstall the cylinder with new gaskets and DON"T change the rings for new ones and DON"T deglaze the cylinder. When you go to install the cylinder, you'll end up indexing (rotating) the rings and now you have in an exaggerated sense an oval bore with oval rings and the 2 ovals don't line up. Expect high oil consumption, lower compression, excess piston blow by on the compression stroke that is now forcing the oil film off of the cylinder walls. In extreme cases, you'll seize a piston.

To do this job right, you really should seek out a quality automotive machine shop that has a Sunnen Precision cylinder block Hone and pay the man to hone the cylinders. A Sunnen Precision Hone will true the bore round to within .0001" and give the new rings which were machined round a good surface to seat in to. If we were dealing with chromium faced rings, this would be a must do phase of a rebuild. The chromium is only a couple of tenths of a thou thick and won't seat in at all. The cylinder liners must wear in to the ring surface and that can take 30,000 - 50,000 miles before they have fully seated. Back in the 1970's Chrysler would not fix an oil consumption problem unless it was over a quart of oil consumed in 500 miles due to chromium faced piston ring seating issues.
If you decide to look in to this type of machining you may stumble across the use of torque plates that are bolted to the block to simulate the cylinder head being bolted on which distorts the cylinder block. This would be for cast in place cylinder liners. In our case, we have wet liners which "float" in between o-rings top and bottom. as the cylinder head is bolted down the distortion is applied to the cylinder block and has little effect on the cylinder liner itself so in this case, we can get away without using a torque plate.

3 stoned expansion hones - throw them out
Ball hones for deglazing - throw them out too

If your going to do this kind of work - Do it right. The benefits out way the costs. As an Automotive Technician, I got exposed to this type of machining work during my school training portion of a 5 year apprenticeship. An Automotive Machinist Apprenticeship was a 3 year program, so what I'm trying to tell you here is that there's more to doing a "ring job" than meets the eye. After finishing my Automotive Technician I switched to the Nuclear industry. My first 6 years as a Machinist Fitter, then 6 years as a Pipe fitter Welder, then 20 years as a Supervisor over Operations, Maintenance and Engineering in a Nuclear Waste Facility. Held 703 different qualifications in that career. So I guess I may have been exposed to a lot of industrial technical stuff Not much escapes me.
1980 KZ1300 B2 converting to an A2.

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Aftermarket piston rings 7 months 3 weeks ago #21629

  • McBoney
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Thanks for the comprehensive explanation Kawboy. Impressive mechanical history you have, more than 700 qualifications! Wow!

In comparison; I have but one tax law degree, that was enough exams for me.... :unsure: :)

I guess to sum it up I have (unwittingly/instinctively) done the right thing: Get a decent (second hand) block and pistons, got the block honed and skimmed, new piston rings, and the pistons will go back in 'their' cylinder (the honer numbered them according to which cylinder they came out of).

Phew!

And not having chromium-covered rings is a good thing as then both rings and bore will shape themselves to each other, whereas with Chromium rings, only the bore will wear to shape.

Paul
Six-Pot-Cafe in the making...

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Aftermarket piston rings 7 months 3 weeks ago #21630

  • StanG
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Great write up Kawboy! Thank you. I asked for it to have it concise and coming from authority. It alignes with all I've learnt in theory, my limited practical experience, and second hand knowledge from people who know more than me.

3 stoned expansion hones - throw them out
Ball hones for deglazing - throw them out too


This is a great point when it comes to ultimate precision. But it has been practiced by many, and worked within acceptable limits. The last time I went to the shop where they did the deglazing for me, I saw a whole wall mounted panel with those types of hones. I'd say most were ball hones. I know my father was using both types on ships. I've heard stories of an engine brake down in the middle of nowhere, these tools were what fixed the problems and took the ship across the globe safely. I'd say definitely not an ideal way to go putting a small performance motorcycle engine together, but I wouldn't completely dismiss them altogether. That's all I'm saying. A real DIY guy on a real tight budget wanting to ride an old bike instead of scrapping it, would definitely be able to put some miles after such a job. Definitely not recommended if looking for a long lasting great precision rebuild, as you said.

Speaking of the sleeve and ring profile. They rotate, but just like you said, stay somewhat oval. The particulars of it intrigue me. Do they actually make it a 360 over time, back and forth, or because of the oval shape, tend to go back and forth withing that parameter? The porous nature of cast iron would suggest easiness for reshaping. That would make sense, in terms of re-using - if they would have freedom to go anywhere finding their sweet spot eventually, withing service limits of course! That's where the worry is I gather.
No use having 'broken in' rings if they don't seal.

To sum it up, the action plan of rebuilding is pretty straight forward to me. Clean, clean and clean more, save money, let a pro machinist with proper tools do their job.
I am a do it yourself kind of guy, but some things are just unavoidable due to specific expertise and tools. This little convo gives me even more peace of mind and less guilt designating money towards outsourcing certain tasks and feeling like a failure that I am not doing them myself!

Thank you!
1982 Kawasaki KZ1300 A4
>>> Need a 79 - 82 frame with title.

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Aftermarket piston rings 7 months 3 weeks ago #21633

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Just to be clear, piston rings do not rotate around in the cylinder. If they did all kinds of shit could happen. The ring ends should never be located on the thrust sides (front and rear) of the piston. The top ring and second ring ring ends should be located directly opposite each other. The oil rings should have all of the ring ends staggered. Once all of the ring ends are located and the piston installed, the rings don't move around.

On 2 strokes there is pins in the piston ring grooves to ensure that the rings don't rotate and get ring ends hung up in the cylinder ports but in reality, the rings shouldn't rotate.
1980 KZ1300 B2 converting to an A2.

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Aftermarket piston rings 7 months 3 weeks ago #21634

  • StanG
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I know Kawboy, that's how they are instructed to be installed. But they do move. Maybe until settled? There is no way I could imagine a floating piece of steel suspended in oil just sitting in one place at thousands per minute of revolving kinetic force. And that's way bigger number than simply counting shaft rotations. Am I just barking up a wrong tree or do you really have a scientific research backing up the no movement info? Valves rotate, and I know the forces are quite different. Perhaps irrelevant. Cylinders become somewhat oval, and rings no doubt slowly find their best fit. With wear, perhaps they like one position so the whole set up is somewhat always in place. But until then, before the kinetic forces, the frictions and viscosities push the rings and the whole assemblies towards that best minimum friction and best seal configuration, I'd imagine all components try to wiggle their way around.
1982 Kawasaki KZ1300 A4
>>> Need a 79 - 82 frame with title.

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