Burning oil after installing new piston rings

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  #1  
Old 05-01-10, 04:12 AM
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Burning oil after installing new piston rings

Hi.
I've installed new piston rings in my old Briggs&Stratton lawnmower (model # 95902). 3 HP engine or something like that. 65.09 mm piston.

At first, after testing it at home for about ten minutes, on easy low grass, it did not smoke at all, but yesterday I went to my aunt's house and tried it there on much thicker and higher grass and after I checked oil today, it's more than half gone (oil dish takes about 0.5 liter of it, so it must have burned around 0.3 liter in about hour of work).

I've noticed blue smoke but only when the grass was higher, when the engine was at maximum stress, I haven't noticed it when it was cutting smaller or less thick grass.

When I was installing rings, I watched to orientate them properly (gaps in 120 degrees from each other), but I'm not sure if it have moved when I pressed it with this tool to fit rings to cylinder bore(don't know it's right name, I'm from Croatia):
http://vedris.com/hrvatska/images/up...nje-potenc.jpg


Now, I'd like to know could this misorientation (if existed), cause this much oil to burn?
Or could it be just because the rings are new and aren't "nested" quite well yet, maybe it'll stop burning oil after few more working hours with new rings?

Or is there a bigger problem and it won't go away?

I've checked the cylinder bore for deeper scratches and there were some scratches, but not that deep. I took the engine to a guy who has more grasp in engines then I do and he said that new rings should do the trick to stop it from burning more oil.

Here are few pics of the engine before I installed new rings:
pics.rar
 
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  #2  
Old 05-01-10, 08:28 AM
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No pictures from that site, but loads of annoying advertising.
 
  #3  
Old 05-01-10, 08:41 AM
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it's a packed up rar file dude.
just wait few seconds while the download link loads (it's in the middle of your screen to the right, you'll see the "Processing download link" message where it'll appear secs later).

unrar the file and check the pics.

but you don't even have to look at pics to answer my question, at least partially.

thanks in advance, anyone.
 
  #4  
Old 05-01-10, 09:54 AM
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It could be a couple of things. It looks like you honed the cylinder before you installed the rings and there doesn't look like a ring groove at the top.

This being the case you could have oil coming in past an intake valve seal/stem guide or the lower end of the cylinder could have too much run out = it has become oblonged with wear. The egg shaping would occur in a line across the crank line. The latter could be checked by sitting a good ring in the bottom of the cylinder within the travel of the piston rings and check the ring gap there and see if any light is passing along the outside of the ring.

The gap orientation isn't likely the problem. That relates to blowby issues and localizing cylinder wear in the circumference of the cylinder.
 
  #5  
Old 05-01-10, 10:33 AM
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First of all, thank you for your answer, I appreciate it. I will try the light test on monday.

I've got few questions more though.

1. what gives you idea I honed the cylinder? I didn't do anything to it. All I've done was just changing rings and putting engine back together.

2. I've tested engine today just in idle mode and noticed somewhat different behavior than first two days. I now can see small amount of bluish smoke coming out even on idle. Also, something what wasn't happening before yesterday if I recall correctly, the engine doesn't have 100% steady rythm and sound. It's like it's working under different amounts of stress in regular intervals of around second of two (normal sound for two seconds - a bit different sound for two seconds - again normal for two seconds - and so on and on).

What could this engine sound differences mean?
I fixed the butterfly valve (for air intake) so it can't move anywhere.
 
  #6  
Old 05-01-10, 11:00 AM
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In one of the pictures, looking across the top of the cylinder it appeared it had been honed, not with a cross-hatch, but with with a straight stone.

However, if you didn't, you should have and I would add that to the list of possibilities. In fact I would move that to the top of the list. You can rent those from an auto parts store. Don't reassemble the engine until the cylinder has been honed, even if the run out is OK.

A lot of the irregularity you're seeing has to do with the varying fuel/air/oil mix you're delivering to the combustion chamber. That won't be fixed until the oil is out and the compression is stabilized at an acceptable level. What you're hearing is a typical surging. You'll get that in a normal engine which is experiencing lean fuel mixture.
 
  #7  
Old 05-01-10, 11:19 AM
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Thanks again for your reply.

I've recorded a short video of the engine running and it appears more smoke than I originally noticed and this time it did not sound irregular as it did to me before.

I don't know, you judge it if you hear any difference.

Anyways, if you have anything more to add after you see it, I'm eager to read.

Here's the vid:
drop.io jdftvnp

thanks again for your help, it is much appreciated!
 
  #8  
Old 05-01-10, 11:35 AM
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Yup, for now, don't think it to death, just do the cylinder work and stick it back together. It's not doing that badly. Probably, unless the runout is way off, just honing the cylinder may take of everything.

If you can't get your hands on a cylinder hone, get some 320 grit emery cloth, cover the crank well with plastic, and scuff up the cylinder walls with the emery cloth. Then clean everything off with soap and water, wipe it all down with gas or preferably diesel, oil it back up with a light coat of motor oil and stick back together. That will probably get you by if the other stuff isn't around.

Is the mower in Croatia? What kind of stuff do you have over there in auto parts stores? Do you have carb cleaners, like Sea Foam? And what do you have for gas?

You'll get the mower going soon. Hang in there.
 
  #9  
Old 05-01-10, 01:58 PM
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alright, I'll do that, thanks for the help again!

regarding your questions, yes the mower is in Croatia, unfortunately, I'm not much into engine stuff so I don't really know what kind of stuff we have in auto part stores, but I'm sure the supply doesn't differ much from what you have in your stores, since all the stuff is probably coming from same or similar sources (to fill your and our stores, both).

By doing quick search online on pages restricted to croatia, I've found people mentioning on forums this SeaFoam carb cleaner, but no one said where he bought it from and I can't find it in online stores.
However, I've found this type of carb cleaner:
Moto Bencony

it's price is 75 Croatian Kunas or about 15$ for a 400 mililiter can (Silkolene carb cleaner).

if you're thinking of getting stuff from here cheap, think again, it's not the price which matters, but the shipping costs, which would rise to around 50+ USD, because of the stupid obsolete postal services working in here, there isn't much serious competition (although I heard fedex is working here as well, but I think all of the services are about the same price, too much).

Maybe if you could get someone who ships abroad, like a store, or a person who sells big.
Maybe I could help you find these informations if you'd need them.

Anyways, this place has been flooded with "western" products (probably made in the east like everything is nowadays) for years now, so you could probably find here most stuff you'd normally find there, it's just the matter of where you'll find it or how easy (depends on how special or unusual the product is, cause some stuff probably can't be found in large malls, only in specialized stores).

As for gas, we use Eurosuper95 gasoline (95 octanes), Eurodiesel (those two are most common car fuels) and some other derivatives, Super98, or Carrera BS 100 (octanes) and such.
If I'm not mistaken, I think we in Europe use pretty much fuel of greater quality than you in USA, but the prices are also "pretty much greater".
For instance, a gallon of this most common gasoline, here in Croatia is about 6 bucks.

Got any questions? shoot.
 
  #10  
Old 05-01-10, 02:18 PM
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I don't think I would worry about the carb cleaner just yet if they soak you for 15$ a can. The 95 octane on an engine that runs well on 87-89 octane would pickup a little performance from advancing the ignition timing since the 95 octane likes to burn a little slower, but it's no big deal on what you're dealing with. That coil is pretty well set where it's at.

Once you get the cylinder in shape and run it a little, I suspect it'll be doing a good job for you. If you have to use the emery cloth, sweep the marks around the cylinder and down at a slight angle (don't rub in one place on a small scoring - stay even) and get all the residue out of it.

Take care
 
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