removed pistons and checked rings by inserting them in the cylinder and measuring gap with feeler guage. rings are worn, but cylinder has no scarring.. do I need to order regular set of rings or oversized ?
question about piston ring replacement
- Thread starter bjohnson
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85Hokie
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BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
What was the gap ?
What are specs on gap?
Micrometer the bore both ways?
How much ridge?
Shoot back some numbers
North Idaho Wolfman
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It's not normal that the rings are worn, it's normal for the cylinders to be worn.
So your going to need to check the bore of the cylinders.
If it's sleeved it going to need a new set of sleeves and possibly new pistons too.
So your going to need to check the bore of the cylinders.
If it's sleeved it going to need a new set of sleeves and possibly new pistons too.
coachgeo
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L225 w/woods Few Mowers & Back Blade, D722 in Motorcycle (Triumph Tiger), LMTV
Can the same engine come in sleeved or unsleeved from the factory? Curious cause for my L235 I see both rebuild kits with sleeves and unsleeved being sold. If sleeving happens in rebuilds... when do you sleeve and when do you bore out and go oversized piston/rings?
North Idaho Wolfman
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Yes a lot of older Kubota engines can come in both sleeved and unsleeved.
If the wear or damage is to great to bore and oversize then a sleeve is a good answer.
If the wear or damage is to great to bore and oversize then a sleeve is a good answer.
coachgeo
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L225 w/woods Few Mowers & Back Blade, D722 in Motorcycle (Triumph Tiger), LMTV
What is best for longevity? Sleeve or oversize? My understanding is the #1 piston in general is the downfall of the older Kuobta engines. Not sure what it is about this cylinder, thinner cylinder wall, last in the path of lube and thus is not lubed as well orrr?
Measuring the ring gap is not a way to determine ring wear. While yes, the gap would increase as the rings wear, one has no way of knowing what the original gap was when the engine was assembled. So, what you perceive as wear due to an oversize ring gap, could actually be very close to the original gap when it was assembled. Unfortunately, you would have no way of knowing what they were set at during assembly. While the rebuilding specs state clearances, in the case of rings, the minimum clearance is the most critical. The metal swells as it gets heated and if the ends are too close the gap can close and the ring can bind in the cylinder. The max clearance isn't as critical. While the spec should have been followed, I've seen engines where the gap was significantly beyond spec in size and it didn't create any issues.
Wolf is right, more normally the cylinders are the measurable wear point.
Usually ring issues show up in one of three instances:
Either the engine was overheated and it got hot enough to take some tension out of the rings, it was run with a loose or missing air filter, or it has a fueling problem that is washing the cylinder walls and preventing the rings from seating properly (rings aren't actually worn at all).
If it got hot enough to take tension out of the rings, the bigger concern would be cracking of the head or block, or a blown head gasket (showing as low compression in one or more cylinders). If it got dusted, then a hone and new rings will usually cure the problem (assuming the bores are still in good shape and mic out within spec). If it's a fueling issue, cure the excess fuel and often the rings will re-seat.
As requested above, you need to mic the bores in both directions near the top to determine how much wear and how out of round they are (mic below the ridge if there is one). It will tell you how worn the bores are and how to proceed next.
I believe that block is sleeved. The rebuild kits come both ways because often guys won't re-sleeve the unless absolutely necessary because it's more expensive. No point in buying new sleeves and having to pay to have them installed and machined if they're not needed. Often the existing sleeves can be bored .5 mm oversize and it will be just fine. That's why you'll see rebuild kits offered in oversize. One really only needs to re-sleeve if one wants to go back to the original bore size for some reason, one finds a crack in an existing sleeve (remember my overheating comment above), or if the existing sleeves are worn past the point of being able to be bored oversize.
Please keep us posted on what you find.
Good luck,
Steve
Wolf is right, more normally the cylinders are the measurable wear point.
Usually ring issues show up in one of three instances:
Either the engine was overheated and it got hot enough to take some tension out of the rings, it was run with a loose or missing air filter, or it has a fueling problem that is washing the cylinder walls and preventing the rings from seating properly (rings aren't actually worn at all).
If it got hot enough to take tension out of the rings, the bigger concern would be cracking of the head or block, or a blown head gasket (showing as low compression in one or more cylinders). If it got dusted, then a hone and new rings will usually cure the problem (assuming the bores are still in good shape and mic out within spec). If it's a fueling issue, cure the excess fuel and often the rings will re-seat.
As requested above, you need to mic the bores in both directions near the top to determine how much wear and how out of round they are (mic below the ridge if there is one). It will tell you how worn the bores are and how to proceed next.
I believe that block is sleeved. The rebuild kits come both ways because often guys won't re-sleeve the unless absolutely necessary because it's more expensive. No point in buying new sleeves and having to pay to have them installed and machined if they're not needed. Often the existing sleeves can be bored .5 mm oversize and it will be just fine. That's why you'll see rebuild kits offered in oversize. One really only needs to re-sleeve if one wants to go back to the original bore size for some reason, one finds a crack in an existing sleeve (remember my overheating comment above), or if the existing sleeves are worn past the point of being able to be bored oversize.
Please keep us posted on what you find.
Good luck,
Steve
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How many hours are on the unit?
Did you do a compression test on it? What were the readings?
Does it have a lot of blow-by?
Is just a case of lots of wear or did something else cause the ring issue that you know about?
Basically trying to get an accurate picture of why you think its the rings that are the problem???
Did you do a compression test on it? What were the readings?
Does it have a lot of blow-by?
Is just a case of lots of wear or did something else cause the ring issue that you know about?
Basically trying to get an accurate picture of why you think its the rings that are the problem???
Measuring ring end gap only applies when installing new rings. Using bore guages is the only way to get a true measurement.
measured the cylinder bore in three different positions, factory spec is 2.992. I measured 2.997 and measured 2.993 at the ridge. placed compression ring in cylinder and measured gap.. factory specs are .25 mm to .40 mm allowable limit 1.25mm.. my measurement was 1.52mm