Pistons?Rings?

I kinda doubt they do, cylinders wear out of round, so once it's oval just a bit, the ring is going to wear into the same shape, I doubt they'd move after that... I've only heard one person say they don't move, and he was a tool&die guy who was into bikes, so more experience in terms of fine measurement and mechanics, but that applies to bikes just like everything else
 
Foudn this on another forum:

"Rings rotate. Factual data is a dangerous thing. When I ran Speed-Pro we had lab data that proved it. Use radioactive pellets embedded in rings to see how fast on the dyno. Turned out to be around 10-12RPM, but completely at random - sometimes they reversed themselves.

Movement was just considered to be due to variations in bore finish and profile. A poor hone job can have deep grooves in one direction and shallow ones in the other - that'll cause the rings to spin rapidly in the grooves and they will wear out very quickly. Gaps lining up is usually bad bore profile - an irregularity in cylindrical shape."
 
Found this as well ADC:
"I found a 1946 aeronautical study where they were investigating oil film thickness on piston skirts and commented on seeing ring rotations of 1 RPM at 1000 engine RPM. They were observing through a Pyrex cylinder so crosshatching is pretty well ruled out.
"
 
well regardless as to if the rings spin or not.

This.

20130824_144136.jpg


if anyone of you wants to follow the rest of the build it will be getting posted back in the build thread now that the motor is together.

http://www.dotheton.com/forum/index.php?topic=51695.0

thanks to EVERYONE that helped in this thread especially ADC and CPJ

Dustin
 
I'm pretty sure I originally posted about rings rotating @7rpm, which they probably do when motor is new but cross hatch isn't an explanation when motor is bedded in, cross hatch has gone.and cylinder is completely shiny.
It's much more likely caused by differential expansion of cylinder, combustion pressure, lack of combustion pressure plus torsional of ring, etc, etc?
I know on engines where rings are pinned in position Usually two stroke but some industrial) the center and ends wear more than the 90 degree position from gap
 
teazer said:
The idea is to set the rings so that the end gaps don't line up. If/when they do there's a some leakage past the rings. As PJ mentioned, rings rotate in use. I want to say it's around 7rpm but I don't recall where I read that.

So you guys all agree now? :)
 
crazypj said:
cross hatch isn't an explanation when motor is bedded in, cross hatch has gone.and cylinder is completely shiny.

I have torn down some high mileage engines that still had cross hatching. I pulled the head from a Honda Accord with 113,000 miles. (I had to do a valve job due to a failed timing belt.) The cylinders were perfect, and still had the cross hatching. Recently, the CX500 that I am working on had 14,000 miles and the cylinders still had the cross hatching.

With modern lubricants and proper plateau honing, there is much less ring and cylinder wear and the cross hatching is present for a much longer time. Think about how we used to consider an automobile engine being close to worn out at 100,000 miles. These days, most engines are still going strong at 300,000 miles.
 
I'm glad I found this thread. I was going to ask what I needed to do for my cylinder walls.
They look similar to your's Duggyb with the rust from sitting... but probably a little worse.
 

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Even after honing I wasn't able to totally get rid of the pitting.
I can barely feel it with my fingernail.
Will I be able to hone this out if I keep going?
Would it wear out the rings quickly if I didn't?
 

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Rings will probably 'flutter' and crack way before they wear out.
If you can feel grooving with fingernail it means it's probably 0.001" or more, the least that will happen is it's going to smaoke real bad.
Should be easy enough to haggle an eBay seller with similar problem then swap liners from 'good' side (something with chipped or broken fins will be even cheaper.)
A new liner is around $60.00 so anything under $40.00 shipped would be reasonable

Here's one but it will need a re-bore :(
http://www.ebay.com/itm/Honda-CB360-CB-360-engine-cylinder-jugs-cylinders-/400402827696?pt=Motorcycles_Parts_Accessories&hash=item5d39de49b0&vxp=mtr

Here's a better one, and it's cheaper
http://www.ebay.com/itm/74-75-76-Honda-CB-360-CB360-engine-cylinders-jugs-cylinder-set-/310659772112?pt=Motorcycles_Parts_Accessories&hash=item4854c3eed0&vxp=mtr
 
no and yes
the only thing you can do with a home shop type hone is glaze breaking to prepare a cylinder that is in good shape to accept new rings
when you get to where you actually have to remove some metal a precision hone must be used
the problem being then you most likely will be too far oversize
the cylinder/piston/rings interface is the very most important precision thing on an engine
don't skimp you will regret it
 
Thanks PJ, but this one is off a '73 CB450.
What is a reasonable rate to have it bored and honed?
I guessing it just depends where you're located and what
the machinists are like in the area.
 
Thanks xb33bsa. I'm probably will go ahead and take it to a shop and get it done.
Hopefully they can get out the bad spots without going oversized. I bought new
standard rings and don't want to have to buy another set. :p
 
Doh, I missed that bit ::)
I would still look for a liner to swap out, your probably looking $120.00+ for pistons (around $120 or more each for Wiseco)
and whatever boring costs - anything from $35 ~$75.00 a hole
I haven't tried it but believe 500 twin cylinder will fit 450?
 
nah, you didn't miss it, I just didn't mention it.
So why swap out the liner instead of just boring?
My pistons are good though. Their skirts didn't have any bad scratches or scoring on them.
 
...because once the cancer starts it never gets better and its entirely possible that a single overbore won't clean out the cancer . At the least a re ring will smoke like a freight train at worst the rings will snag in the rust and catastrophic metallurgical destruction will ensue ...

~kop
 
It's just a lot cheaper to swap out a liner then mix and match whatever pistons you already have. If money isn't a problem bore it (I would bore it even though I was laid off over 2 yrs ago)
I forget not everyone is as broke as I am ;D
 
Thank you for the help guys.
I'm going to take it to a machinist to see if he can hone out enough to get the
pitting out while still keeping it within the serviceable limit. The manual states that
standard value is 70.0 - 70.01mm and the serviceable limit is 70.11mm.
We shall see.
 
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