Do you Reuse or Replace Rings

[oliver2-44 10,367]

So I've always been taught by old timers... If you pull a piston out of an engine cylinder bore (for some reason, and the bore is good) you still have to hone and re-ring it.  I've never had a good explanation why, just don't reinstall used rings.  So I've never reused rings.   But recently I read something that led me in the direction that it was OK to pull a piston and put it back in with the existing rings.  Of course you can't always believe everything you read.  So I'd like to hear what everyone does and why, and maybe learn the real reason to do it one way or the other.  Thanks.

 

[ebinmaine 70,733]

I have almost zero real world experience in building engines. I've taken quite a few apart over the years.

 

I don't ever recall hearing or reading that you specifically CAN'T put used rings back in but I've also not done a ton of research on the subject.

My impression has been (right or wrong) that something with minimal wear on the piston and bore could be reinstalled.

 

I'll be curious to see what the answers are here...

[Achto 28,777]

Rings seat or wear in when you run the engine. Once you pull them out you can never get them back in the exact orientation that they were in. This will cause them to leak, oil & compression. Besides this fact, you already have it apart why would you not change them?

[953 nut 57,902]

Your piston rings are made of cast iron and will wear just like the cylinder walls. The Kohler manual clearly states you NEVER reuse old rings.

[peter lena 9,088]

@oliver2-44  think that for what's involved to get to the rings , that they should be replaced , also verify the piston ring , set area for being like new clean . for the cost of a ring set , and the labor time to replace them , you would be foolish to try and reinstall rings to the original setting. whenever I have had to work my way into a tight spot , going new with parts , is the way to go , just my own experience, pete

[pacer 3,175]

I'm with the rest of the group, I replace them. As mentioned, if you got it apart, why NOT! With the influx of the import rebuild parts being crazy cheap, the last 2-3 engines I went into I just went ahead and got one of the 'kits' (On a side note here, I've been using them for some 5-6yrs and I have NO complaint with them)

 

Well, I have to say that when I was a kid and at 14yrs bought a Cushman motor scooter for 40$, I would take that thing apart and put it back together... just because! I was fascinated by it - and til this day, at 80yrs, I still get a thrill out of tearing into an engine.

[Lane Ranger 11,125]

Give those old rings to your local blacksmith!  They are made of good steel they can reuse for making neat things! 

[oliver2-44 10,367]

8 hours ago, Achto said:

Rings seat or wear in when you run the engine. Once you pull them out you can never get them back in the exact orientation that they were in. This will cause them to leak, oil & compression. Besides this fact, you already have it apart why would you not change them?

That essentially what i had beet told by old timers.

 

8 hours ago, 953 nut said:

Your piston rings are made of cast iron and will wear just like the cylinder walls. The Kohler manual clearly states you NEVER reuse old rings.

its good to see this in writing, it clarifies what I've always done, just never had a iron clad reason why.    

[ebinmaine 70,733]

3 hours ago, oliver2-44 said:

iron clad

That's a good one.. 

[Snoopy11 5,717]

On 8/8/2021 at 10:58 PM, oliver2-44 said:

So I've always been taught by old timers... If you pull a piston out of an engine cylinder bore (for some reason, and the bore is good) you still have to hone and re-ring it.  I've never had a good explanation why, just don't reinstall used rings.  So I've never reused rings.   But recently I read something that led me in the direction that it was OK to pull a piston and put it back in with the existing rings.  Of course you can't always believe everything you read.  So I'd like to hear what everyone does and why, and maybe learn the real reason to do it one way or the other.  Thanks.

 

I usually don't even pull the piston... even when I put new rods in... just to avoid ring gap-bull-crap

 

BUT, yes you can reuse rings... IF the engine is new. If the engine is used... even for a short length of time, rings should be changed, gapped, and lubricated with molly lube. 

 

My engine building experience shows that the above is best policy, particularly since pulling a piston without replacing rings is something that you really don't want to have to open the engine back up again to fix if you start it up and find that you are burning oil or losing power due to ring issues. Also, in case anyone doesn't know, make sure to orient the rings differently on each level, so don't let the gapped positions of the piston rings be in the same orientation. 

 

Orient them such as the following:

 

 

Don 

[953 nut 57,902]

16 hours ago, Snoopy11 said:

don't even pull the piston... even when I put new rods in.

                  How do you replace a rod without removing the piston, kind of hard to get the wrist pin out and replaced in the cylinder!            

[Achto 28,777]

1 hour ago, 953 nut said:

                  How do you replace a rod without removing the piston, kind of hard to get the wrist pin out and replaced in the cylinder!            

 

I have done it on engines that have removable cylinders. Pull the cylinder up high enough to get the wrist pin out but leave the piston in the cylinder. Used this process to change cylinder to case gaskets on Harley's quite often.

 

Don't see it being possible to do on an engine without removable cylinders though.

[pacer 3,175]

18 hours ago, Snoopy11 said:

Also, in case anyone doesn't know, make sure to orient the rings differently on each level, so don't let the gapped positions of the piston rings be in the same orientation. 

 

I knew about orienting rings even at an early age..... but I had a first hand look at what can happen! Some 3-4 yrs ago I got a D200, been outside and was really pathetic, but complete with deck and for $200 I figured I couldnt go too wrong. First thing I always do is just see if one will run and drive (if possible!) Got it running pretty easily with a jury rigged fuel system ---- and WOW, mosquito fogger, big time smoker! Let it run 10 min or so hoping might loosen up and it ran quite smoothly but smoke didnt improve at all  -- nope wasnt gonna happen. So I pull the engine and on getting the heads off was surprised to see really clean cylinders with .020 pistons. When I popped the pistons out it was easily apparent what the problem was - remember this is an opposed cyl engine and the pistons are sideways - the ring gaps were neatly stacked on the BOTTOM!! After further insp, it was pretty apparent that the engine had been rebuilt with a boring out to the .020, every thing was new appearing, just some how was assembled with the rings that way. I ordered up a new set of rings, done a quick hone on the cyl walls and reassembled with special care to get the rings correctly orientated. And, guess what? that thing ran like a ... well, like a rebuilt engine, no smoke at all. Its been my go-to mower now for the last couple yrs and that engine is sweet!

[lynnmor 7,560]

One exception that I have seen was a two stroke outboard motor.  It had three rings on each piston that were oriented with pins all in a row.  Of course two strokes have no oil ring and all those holes in the cylinder walls leave little real estate for ring gaps.

[Snoopy11 5,717]

4 hours ago, 953 nut said:

                  How do you replace a rod without removing the piston, kind of hard to get the wrist pin out and replaced in the cylinder!            

Well... this works on various engines, particularly the ones that I have named above. Duromax, Predator, Tillotson, Massimo, Troy, Champion, Generac, (yucky Ironton)... and many MANY others. It even worked on a Briggs v twin... 

 

This requires internal disassembly removing cam, crankshaft, pushrods, cam followers. Removal of valve cover(S) is necessary in all cases to verify pushrods are in correct positions on rockers. BUT YOU DON'T NEED TO REMOVE ANYTHING IN THE VALVE TRAIN!!! 

 

Before you do anything, though, pull the spark plug, as the compression will not allow you to rotate the engine like you need without the spark plug being removed.

 

Loosen and remove rod cap bolts. 

 

Next, instead of pushing the piston UP though the head (as you would with head removal)... pull the piston with its rod down into the crankcase. Keep pulling down until you see the wrist pin. This is where you need to really be careful, as if you pull the piston too far accidently, you will have to use your fingernails, flat screwdriver or some other small thin device to assist in squeezing the oil rings to get the piston back in the cylinder. Technically, you can remove the entire piston to changed the rod, and put the piston back in from the crankcase, rather than though the head. BUT IT IS 10 TIMES EASIER IF YOU DON'T REMOVE THE PISTON FROM THE CYLINDER.

 

Needle-nose pliers are excellent for taking out the wrist pin clips. Ordinarily, you just have to take out the clips on one side of the piston, and the wrist pin can be pulled out. 

 

Getting the crankshaft out is the hardest part, because the rod (plural on v twins...) have to be oriented in a way that allows the crank to slide out without hitting the crankshaft journals on the rods.

 

Timing the engine properly is a matter of aligning the dots on the crank and the cam. Just ensure that when you pull the camshaft out, you are at TDC, with the dots aligned on the crank and cam. 

 

Next time I put a billet rod in an engine, (which I am hoping to do in my Mark II engine soon), I will take photos...

 

Be aware that if you attempt this on a briggs engine, DOUBLE, TRIPLE check to make sure that the pushrods are in their correct orientation. I won't say why beyond that the intake pushrod can go into the crankcase if there is a mistake. 

 

 

Don

 

 

[Snoopy11 5,717]

2 hours ago, pacer said:

 

I knew about orienting rings even at an early age..... 

Yes sir, same here.

 

Interestingly though, often when you go to remove a piston, the rings are in a different orientation than you placed them. Indeed, I had an engine that had spun rings and blew smoke and made me think that I needed new rings. BUT all it really needed was for the gaps to be re-oriented. Put it back together, been runnin' like a hellion ever since with no smoking...

 

I should say... spinning rings with them all landing in the same orientation is... RARE... to say the least... 

 

Some new engine builders may not know this, thus why I think it productive to disclaim this information!!!

 

Don

 

 

Edited August 12, 2021 by Snoopy11

[Achto 28,777]

Generally I place the gaps on my compression rings 180° from each other and then stager the oil rings so that they do not line up with the gaps on the compression rings. No gaps should ever be on the thrust surfaces of the piston.

[Howie 899]

And then as they run they turn in the cylinder. They do not stay stationary they rotate.

Learned that from a Briggs representative at an update seminar yearas ago and just

had it reiterated by an engine builder just this week.

 

[tom2p 2,394]

if you pull it apart makes sense to replace the rings 

 

standard iron cylinder liner - prob should also hone ?

 

chrome bore or nikasil (or similar) plated liner - don't touch the bore / just install new rings  (can use a mild scotchbrite pad to deglaze liner)