In frame honing of good bores.

[kubotafreak]

I know how controversial this topic seems to be. The purpose is more for those that would like to see an example of my technique. Obviously it would be insurance to JUST REPLACE EVERYTHING. Sometimes, cost, availability (discontinued parts), ease of access, time, are all factors on why you wont just replace all the parts with new. I have seen way too often good engine parts thrown out due to over-disassembly. OEM build quality is many times better than even experienced mechanics abilities. I do not unless availability dictates, use non OEM hard engine parts to replace/repair. That is not worth my time, and money. This is not a dealer level repair, as your shop time would not see any profit. Enough with the disclaimer for Karens... Now for the Dr. Jekyll repair you have all been waiting for.

This seems to be a common finding for small engines. Many mowers, small tractors, and other small engines can easily glaze cylinders if they run hot for any amount of time. The nature of their run environment makes it too easy to run hot. Chaff, grass, and dirt/dust can clog radiators. Many new owners of OPE do not know how to maintain it efficiently. The engine candidates would only be those with good pistons/bores/rings that have low engine run hours(ring wear less than 1000hr). I use this primarily for engines that need the head lifted(for rework), and to freshen up glazed bores. Good bores measure within spec at both top(1/4" down), and bottom of bores measured in at least two crossed positions. You must have some good bore gauges, and a caliper to measure this.

 

[kubotafreak]

Clean and mask off all the cylinders, and deck surface. This is to prevent debris from entering the water and cam/lifter jacket. Position piston at the bottom of the bore. I inject grease with a needle greaser to get it packed in around the piston crown.

 

[kubotafreak]

I use wd40 to lube the ball hone. Make sure it is sized appropriately for your bore. Run it at about 1/3rd trigger speed on most hand drills. Ensure to run the drill as the hone enters and leaves the cylinder. You are trying to run the hone at the same rotational speed, as you are in and out of the bore. This creates a 45' crest angle on the cross hatch.

 

[kubotafreak]

You should only run the hone long enough to remove the carbon trace, and get a good uniform hatch pattern. Usually no more than 15-30 seconds. Very little if any measurable material is removed if done correctly. I clean the bores with a carb cleaner soaked paper towel. This is the messy part as it takes several new towels to get the bore clean 4-6. Once the hole is clean, spin the piston up a 1/2 inch then back down to get the grease ring. Once you solvent clean the cylinder, then I use wd40 to wash lube the cylinder.

This is the most controversial part of this process. I know you will never be 100% surgical here, but if you can get the 99%, that is good enough. Think of all the carbon packed in those rings anyway. And by the way, you will notice the wd40 breaks up all that carbon/grease when you move the pistons up and down a few times. It is not abrasives, you already removed that...

 

[kubotafreak]

Hopefully this will serve some of you well, and also give you some confidence to bring something back from the dead. Tearing into the lower end and removing a piston from the jug at minimum will be a ring set, and if your staying true to your 100% replacement policy, some connecting rod bolts, and bearings. $110 for this particular engine per cylinder.

If you do some research, the last 10% of the bore not honed will not amount to much. First of all it is considered the no wear zone. So the original hatch is still there, as proven by visual, and measurements. The compression does not start escaping the piston ring interface until about the half way point. The majority(like90%) of engine wear is at the uppermost 1/3 of the cylinder. This again can be seen visually, and with measurement. So if you have a bore and the top measures out the same as the base of the cylinder, you have no bore distortion short of what it left the plant with. This particular engine measured 94.0mm on 11/12 points measured. The one deviation was 94.02, and I attribute that to manufacturing, due to the fact it was at the base of the highest compression cylinder. This engine had 250psi dry-320psi wet cylinder 1, 150psi dry-180psi wet cylinder 2, and 200psi dry-200psi wet cylinder 3. The culprit for this engine appears to be leaky valve stem seals. Probably caused by overheating the rubber. This made the exhaust ports very full of oil/carbon deposits to the point of limiting airflow. I will update the compression once assembled.

Pic of head below cylinder 1 is top. TSC company sells PSC1000 low voc solvent cleaner. It works well for the anti cootie world we live in.

 

[Jim L.]

Thanks for sharing a good tutorial with us. Certainly shows another path to get it working when parts are not available or economical.

 

[ruger1980]

Remind me to never allow you work on anything I own!

 

[kubotafreak]

Remind me to never allow you work on anything I own!

Well don't stop there, how would you do it?

 

[ruger1980]

I would pull the oil pan off and remove the pistons. You are almost there with the head off. Why do a job half assed?

 

[ruger1980]

But I would clean the ridge first and probably hone with a fixed hone and surface hone with the flex hone

 

[kubotafreak]

But I would clean the ridge first and probably hone with a fixed hone and surface nose with the flex hone

If there is a ridge you more than likely have enough wear to not warrant this procedure, or even the one you describe, which will remove even more material. I don't even own a ridge reamer. Do you know why? Because since the advent of moly rings that amount of wear is almost a thing of the past. But if you actually do own one I would like to know what brand because a man can never have too many tools. I guess I could use it for the junk engine that might have a ridge so big you cannot remove the pistons, or better yet as a shelf piece.

 

[ruger1980]

If there is a ridge you more than likely have enough wear to not warrant this procedure, or even the one you describe, which will remove even more material. I don't even own a ridge reamer. Do you know why? Because since the advent of moly rings that amount of wear is almost a thing of the past. But if you actually do own one I would like to know what brand because a man can never have too many tools. I guess I could use it for the junk engine that might have a ridge so big you cannot remove the pistons, or better yet as a shelf piece.

What diesel engine manufacturer uses Moly rings? None that I am aware of.

You mention removing material which is what you are doing and also doing so in the upper half of the bore which experiences the most of wear.

If an engine has a loss of compression simply honing half of the bores will not correct it.

 

[foobert]

Remind me to never allow you work on anything I own!

I would pull the oil pan off and remove the pistons. You are almost there with the head off. Why do a job half assed?

Apparently, a full paragraph of disclaimers for passive aggressive Karens wasn't enough...

 

[kubotafreak]

What diesel engine manufacturer uses Moly rings? None that I am aware of.

You mention removing material which is what you are doing and also doing so in the upper half of the bore which experiences the most of wear.

If an engine has a loss of compression simply honing half of the bores will not correct it.

Apparently Kubota does... Unless they just like spraying silver paint on the ring edge...
Most rings, oem and replacement are moly coated. It used to be worthy of advertisement, now it is standard practice to have the primary ring coated. If you thought I meant the whole ring was moly, I apologize for the confusion..

 

[ruger1980]

Moly is not silver in color it is dark grey in color. I see no proof in anything you have provided that that any rings shown are Moly coated.

 

[DustyRusty]

 

[William1]

I'm with ruger. The pistons should of been pulled. The complete barrel honed and cleaned. Fresh rings properly installed.
There is now a ridge mid bore (a step in fact) where the honing stopped. As well as any debris lodged down on top of the top ring land.
First step should be a leak down test to see if the honing/reringing is even needed.

This is akin to painting a room and not moving the furniture. There will not be paint behind the couch. Sweeping the dirt under the rug on the hardwood floor. Taking a shower and only washing 1/2 of your body. You will still stink just as much.

'Silver' rings are usually chrome plated and are the top ring. Though in some cases, it is merely a coating (even a 'paint') that wears off in the first few run time minutes.

 

[kubotafreak]

I'm with ruger. The pistons should of been pulled. The complete barrel honed and cleaned. Fresh rings properly installed.
There is now a ridge mid bore (a step in fact) where the honing stopped. As well as any debris lodged down on top of the top ring land.
First step should be a leak down test to see if the honing/reringing is even needed.

This is akin to painting a room and not moving the furniture. There will not be paint behind the couch. Sweeping the dirt under the rug on the hardwood floor. Taking a shower and only washing 1/2 of your body. You will still stink just as much.

'Silver' rings are usually chrome plated and are the top ring. Though in some cases, it is merely a coating (even a 'paint') that wears off in the first few run time minutes.

Don't know if I agree, It would be more like not removing all the base boards to paint behind them. As far as taking a shower, if you took a shower (new build), and got your hand dirty would you take another shower? Any how, fair enough point to make. As far as the mid bore step, I cannot agree. If anything the closer you get to the piston, you will have less action by the ball hone, if moving in a 45' x-hatch. It is simply fact that it remains at the top the entire time, and dips to the lower portion in interval. If you had made the argument that the ball hone wore the bore the slightest bit, in a taper (larger end at top) I couldn't help but agree. The goal is always RMA finish, not actual size change. This again is simply ID measurable with bore gauges. Again assuming the user of the tools, know how to use them. There is an art, and feel to all of this. Most cannot just pick up machinist tools, and get true measurements.

If you think that the honing trash gets past the grease layer, consider changing plugs. How uncontroversial is changing spark plugs on ohc engines? I would bet more debris is introduced by a blind spark plug change. Even if you blow off the plug crown pre-emptively, you should do it again after the plug is broke loose. The debris breaks loose after the fastener is turned. How many people do that? The hone idea is very unconventional to say the least, but if we are objective with the net outcome, risk vs reward. Maybe I am talking to the wrong crowd, I bring dead engines back to completely functional life. I don't just pontificate about some hypothetical scenario that involves unlimited money, and ignored human risk factors. You might be amazed at what level of flatness two kids, and a piece of glass in a third world country can do to a cylinder head. I've seen enough shoddy machining work to make you only want to buy oem new(and check it), or even good used. I have saved many small engines with used lower end parts. Readers are probably cringing now...lol

The ring coating if we are calling it a coating(it is really an edge treatment), is called many names: Chrome moly, moly, cast moly, ductile moly, plasma moly... It doesn't really matter what you call it. It functionally is the same thing (Plasma Moly) counter to the ring base metal. You are correct it is sprayed on the bore edge of primarily top rings. It is sprayed on very thick, and at a molecular pore level. The embedment in the ring edge profile is usually dished shape, so even when the total moly edge wears off, it is still riding on a sandwich of ring/moly/ring. If you are buying rings that have a paint layer that wipes off when assembling the engine, you have cheap rings that are not what I consider Moly, and probably not oem. The above engine had 400 hours, hardly time enough to wear out the ring coating.

 

[North Idaho Wolfman]

What was the bore size that you measured?
With the original compression numbers you state, I would have been more then convinced it needs a complete rebuild.
Curious what you get for compression numbers after your "rebuild".
And the head/valves looks more like piston ring failure than it does valve seal failure.

 

[JohnDB]

There is now a ridge mid bore (a step in fact) where the honing stopped. As well as any debris lodged down on top of the top ring land.

Can you explain a bit more about the step mid-bore? My understanding of the flex-hone is that it doesn't remove appreciable material at all unless you spend hours hanging onto it. Maybe you are thinking of a bar hone?