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Pro Circuit Piston ring orientation

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Getting ready to install this piston in my wife's bike and it only has a single compression ring so I can't really follow the manual on the orientation of the end gaps.

Is there a preferred method of the end gaps, ie 120 degrees apart? Should any end gap be anywhere specific other than the 120 degrees apart?ie top ring gap is under 1st exh valve etc??

thanks!

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It really doesn't matter as long as the 3 end gaps don't line up. The rings will turn on the piston when it runs anyway.

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It really doesn't matter as long as the 3 end gaps don't line up. The rings will turn on the piston when it runs anyway.

That is how I always did it. Make sure that no ring end gaps are completely in line with one another. But, to further speculate on this if I may, why are the manuals so specific on the degree locations if indeed as you suggest, that the rings rotate on their own? It's as if they are insinuating that the rings are not going to traverse around the piston. I'm not doubting you, just questioning the manuals high line profile of importance on ring orientation.:thumbsup: As many times as a piston is going through its' cycles, and say the rings do line up, there would be a noticeable compression loss. How did they design it to where this could not happen? What are the odds of two or three rings lining up anyway? I would think if the rings are seriously out of spec, that I could deduce that it would be one of the reasons for serious ring rotation - but honestly have yet to witness it.

Edited by nokickstandsallowed
Keep getting knocked offline before I finish my comment.

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I doubt the rings spin around the piston while the engine is running.. I properly index my rings to what the piston manufacturer recommends, and when I do tear down, they are always in the same location.

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I doubt the rings spin around the piston while the engine is running.. I properly index my rings to what the piston manufacturer recommends, and when I do tear down, they are always in the same location.

This has me thinking now. I noticed when I did my second rebuild, that the stock piston has a tiny hole for the compression and secondary ring at the precise degree locations of each end gap. I'm surmising that this is to allow for oil drainage back to the case. I did follow the manual specs to the "T" when installing them both plus the oil ring for the second rebuild; but, this time I will be paying attention to see if they changed positions when I do my third rebuild, which I doubt they did now that I have confirmation from someone who properly indexed them and can confirm that in fact they did not move.

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Yes, the rings will turn. They don't spin at 20 mph or anything but the can rotate slowly on the piston mainly due to harmonics in the engine. On a 3 ring piston I install the the oil scrapers with the end gap centered on the skirt. The second ring goes in line with the wrist pin on one side and the top ring is on the opposite side in line with the pin. Rarely do I tear an engine down that comes back out the same way I put it together.

The wrist pin clips can rotate as well. I always put them in with the gap at the top or bottom and when I go back into the engine in a lot of cases they have rotated.

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Yes, the rings will turn. They don't spin at 20 mph or anything but the can rotate slowly on the piston mainly due to harmonics in the engine. On a 3 ring piston I install the the oil scrapers with the end gap centered on the skirt. The second ring goes in line with the wrist pin on one side and the top ring is on the opposite side in line with the pin. Rarely do I tear an engine down that comes back out the same way I put it together.

The wrist pin clips can rotate as well. I always put them in with the gap at the top or bottom and when I go back into the engine in a lot of cases they have rotated.

I still don't doubt what your saying, and I understand they are not going to spin like a top, I wonder why they even go out of their way to even mention in the manual what position to put them in if they are just going to move anyway? And what are the odds that someone who properly indexes their rings is going to pull the motor apart and have the rings be in the same position as when they installed them say six months ago? Think about that for a moment, that would be like hitting the three digit lottery two times in a row. I'm not saying it can't happen either; but, what to believe, what to believe? I realize that they have to give you something to go on and make sure that you don't line the end gaps up. The one in particular that I am having a hard time swallowing, is the fact that you mentioned that the wrist pin cir-clips move also. With so many conflicting reports of how to install those cir-clips these days, I don't even know why I just don't hold my breath and wait for someone to suggest to not install them at all and tell me that I'll have better luck that way.:thumbsup:

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I know for a fact the clips can turn also. I have done way too many freshen ups on engines that I built and it's not uncommon for the clips to have turned. I always put the clip in with the gap facing down and will continue to put them in that way.

The way I look at it, the manual is an excellent guide and I follow all of the important torque specs as well as going by most of the factory toleracances and clearances. Read the valve section in your manual and you'll find they tell you to lap the valves. Everyone knows that you never ever lap a titanium valve!

Putting the rings in the position the manual recommends is fine. I put them in different because in my experience having the oil scraper ring gaps located inline with the piston skirt allows them to go into the cylinder much easier. I've put them in all different ways with no issues, but my method just works better for me during assembly. I'm not saying my way of doing things is the best, only that through trial and error I have come up with the way things work best for me. Luckily I do a lot of engines so I am able to try different things. I keep a log book so I can see what worked and what didn't.

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I know for a fact the clips can turn also. I have done way too many freshen ups on engines that I built and it's not uncommon for the clips to have turned. I always put the clip in with the gap facing down and will continue to put them in that way.

The way I look at it, the manual is an excellent guide and I follow all of the important torque specs as well as going by most of the factory toleracances and clearances. Read the valve section in your manual and you'll find they tell you to lap the valves. Everyone knows that you never ever lap a titanium valve!

Putting the rings in the position the manual recommends is fine. I put them in different because in my experience having the oil scraper ring gaps located inline with the piston skirt allows them to go into the cylinder much easier. I've put them in all different ways with no issues, but my method just works better for me during assembly. I'm not saying my way of doing things is the best, only that through trial and error I have come up with the way things work best for me. Luckily I do a lot of engines so I am able to try different things. I keep a log book so I can see what worked and what didn't.

I was going to ask you what way is best to put the piston wrist pin cir-clips in because of the fact that they move also. (Hint: wasn't doubting you there either) From various extensive articles and threads that I have read, and the manual, installing them with gap facing down or six o' clock position is best because the results indicate that the piston is under the most stress during detonation. The solid or heavier part of clip would tend to want to travel up against the detonating forces and therefore, makes perfect sense to me. Further analysis of this suggestion would also indicate that it would be reasonable to assume that the cir-clips would stay in that position. Again, what to believe, what to believe? If they are moving from there original positions that much, (and those clips fit snug) I would think they were overstressed putting them in and need replacing. Those clips are the one clip that can cost big money if it lets loose.

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I've never had a clip come out but I always pay close attention when installing them. Once I get them in I look at them under a magnifying glass to be sure they are fully seated in the groove.

My opinion on why they move is harmonics or basically vibrations in the engine. Even though I would prefer the clip didn't move I don't think it's anything to be concerned about.

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I've never had a clip come out but I always pay close attention when installing them. Once I get them in I look at them under a magnifying glass to be sure they are fully seated in the groove.

My opinion on why they move is harmonics or basically vibrations in the engine. Even though I would prefer the clip didn't move I don't think it's anything to be concerned about.

I agree that harmonics and engine vibration no doubt cause clips and rings to rotate. I don't think that is your opinion or my opinion alone, I think it is a widely universal and accepted fact of engine dynamics 101.

I think what I was getting at with the cir-clip issue is that those are high tempered clips and if they are closed to far upon insertion, that over stresses them and can allow for abnormal rotation leading to a catastrophic failure. Time and time again, I have read that guys have blamed the position of that cir-clip for their engine failures and believe it or not, they installed it in the widely accepted universal position of 6 o' clock or gap facing down. Later on, they usually admit that they got frustrated trying to put them in correctly and confessed to having squeezed them all the way closed to get them in thereby stressing and fatiguing the metal too much because they closed it all the way one too many times. I can understand that because when I didn't have the proper tool to put them in, it kept popping off the end of the makeshift tool I was using. After about ten tries, the clip was trashed and I ended up buying the right tool. Maybe they just tried to put them in with the wrong tool also, but didn't give up until they got a mangled clip to fit in there -- Who Knows?

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