I've been wondering about doing the same thing myself. Are there any special precautions necessary to stop any residue from the honing getting into the gap between piston and bore? If you seal the gap how do you do that, and how do you wash any honing residue out of the bore without any of it getting places it shouldn't. Also do you recommend a flexible hone or a rigid one? Thanks.
Low Compression
- Thread starter vollr
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kubotafreak
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GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Absolutely.
Buy the correct BRM(flexhone 240 grit) based off bore size. Too large and they tend to damage the deck surface. As far as preventing debris past the rings/piston: I take some light grease and wipe a small ring around filling the piston gap. Wipe off all the excess grease, and clean the bores down with a solvent soaked towel. I take a cardboard circle the size of the piston and place it over the crown to prevent the piston from scratches. When you run the hone, speed is not the goal. You are trying to make fewer deeper hatches in a 45` crest angle, vs the brushed stainless look you will get running high rpm(think sinusoidal). You should be moving the hone up and down in the bore matching the speed of the hone. It is something of an art... Clean the hone with carb cleaner often, and use light cutting fluid or wd40. Try to also run the hone all the way out of the bore as it exits if that makes sense. You don't want to stop down in the bore and scrape it out not spinning. Run only enough to make a good even cross hatch. Once done, I use carb cleaner soaked paper towels to wipe the bore until it is no longer picking up gray debris. Move the piston up and down a few times, clean once more, then oil the cylinder. Sounds like a lot, but it is nothing once you get the hang of it.
North Idaho Wolfman
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Well I might have missed a point or two along the way but it sounds like to me that something is way too tight.
And RTV on a head gasket could easily loose you 100PSI or more!
It's way to thick.
You don't need to even pull the engine to check the pistons if you can get the oil pan off.
Pull the head, pull the pan check ring gap, check piston gap, remove pistons and rods one at a time, if it's set up proper you can spin a Kubota engine by hand without compression on it.
Oh and one tooth off on any of the timing gears it won't run!
And RTV on a head gasket could easily loose you 100PSI or more!
It's way to thick.
You don't need to even pull the engine to check the pistons if you can get the oil pan off.
Pull the head, pull the pan check ring gap, check piston gap, remove pistons and rods one at a time, if it's set up proper you can spin a Kubota engine by hand without compression on it.
Oh and one tooth off on any of the timing gears it won't run!
kubotafreak
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GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
It would not be something anyone would advertise, and I would not suggest it for someone who has never rebuilt many engines. In my eyes it very much depends on if the candidate engine has good bores pistons and low ring/cylinder wear. Think of it as just giving that engine that is young with a bad break in a second chance at life. In my experience many of these low hour Kubotas are just that. Usually a machine gets handed down to a person who does not service the oil, and never cleans out the radiator.
The only issue to me if a piston ever comes out of a bore, is that the rings can never be put back in the exact same place as worn. This to me requires that they must always be replaced if they are removed. Only caveat would be an engine that was never run for any amount of time(say 20 hours). Don't forget that the rod bolts can only be torqued so many times before they are too stretched. All I am really trying to pin point here, is that over disassembly is expensive, and unnecessary. The oem parts are plenty expensive enough as it is. Non oem on engine hard parts, and most gaskets are not worth my time/money. This technique serves me well on small engines. The heads can be removed so easily. If you ever look at moly rings, they have so much material to wear. I would guess they easily can survive 4+ thousand run hours with good oil changes.
Good info! I'll have to pull the engine before the pan will come off. Then pistons will have to be removed and clearances set to spec. This will take me awhile but it has to be done. When I put it back together I'll let everyone know how it turns out. Thank you!
I have, from the shade tree mechanic up the road.
Think on this. What are you doing in honing a cylinder? You are (1) removing material and (2) roughing the surface and (3) only following whatever contour is already there. So where does the iron material being removed go? Down between the piston and the rings. And the cylinder will get slightly larger in diameter, but only above the pistons if they're left in the bore, which means now you have a bore that is larger in diameter in a certain area, and smaller at the bottom. And it'll also have some residual material left in there that was removed from the honing process, which is abrasive. It's about like leaving the air filter out for 20-25 hours use in a dusty field. Also if the cylinder is egg shaped or tapered before honing, unless you buy a really really good hone (they are several hundred to several thousand dollars), you are simply making the egg shape or tapered shape worse rather than fixing the problem.
For those reasons, I don't like flex hones and certainly don't approve of doing it with the pistons still in the block. I have in the past, and it cost me. Thankfully it was my own engine and not someone else's so I had nobody to blame but myself. 2.3L engine in my Mustang. The final fix was to pull the engine back out (again) and send it out for bore. I honed it myself to the cylinder finish I desired based on the piston and ring manufacturer. I have a really good cylinder hone that I used at the dealership for this purpose and it just happens to work on the little 2.3. It is still in the car, and runs amazing-and it has an easy 150,000 miles on it since that rebuild. Originally I went against my own "do it right or don't do it at all" mentality, and figured I'd have to go back into it at some point, I just expected it to last longer than 3700 miles.
I am not nearly as experienced as Hokie, tiger, lugbolt, Wolfman and others here (sorry if I overlooked you professional diesel mechs) ….but It’d be a cold day in hell before I’d put a “spoonful” of oil in a diesel engine to run a compression-test.…because many diesel engines have such close-tolerances between piston/head and valves …as to create an interference/contact between such parts and seriously damage the engine.
My RULE for diesels: NO OIL FOR COMPRESSION TESTS and NO ETHER OR STARTING FLUID unless the engine mfr’r specifically recommends it. (Some diesels do have a starting-fluid provision or adaptor/fitting.…but Kubota prohibits the use of starting fluid/ether in all the Kubota manuals I’ve read. The reason is because the starting fluid/ether may combust prior to the piston reaching TDC and that can be destructive to the engine and bend connecting rods, etc.)
My RULE for diesels: NO OIL FOR COMPRESSION TESTS and NO ETHER OR STARTING FLUID unless the engine mfr’r specifically recommends it. (Some diesels do have a starting-fluid provision or adaptor/fitting.…but Kubota prohibits the use of starting fluid/ether in all the Kubota manuals I’ve read. The reason is because the starting fluid/ether may combust prior to the piston reaching TDC and that can be destructive to the engine and bend connecting rods, etc.)
kubotafreak
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GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Lugbolt,
I can agree all that you described can be major risk factors. However, an engine with less than 400 hours will have little to no descendable bore distortion, than what it was left with after the boring process. All these methods are predicated on experience and correct tools. Many things like the contamination can be mitigated as described above. For any hard parts replacement, all of them should have a rebore, which would require new pistons/rings/lower metal/ hardware. The cylinders wear naturaly in a tapered manner above the oil ring at bdc. Oil supply to rings, ring tension, and ring flutter under max load tdc cause this. Full replacement only seems like insurance to your opinion. The manufacturer publishes max allowable tolerance for many reasons. Ring pressures above half way up the cylinder are the only real compression loss zones. The whole proccess of milling, turning, and boring are way more risky for someone to undertake. Because you really get into the shade tree relm of how to machine metal, vs how the oem manufacturer does it. Many oem parts are heat treated or nitride coated. In my experience lower end rebuild problems exist at a much higher rate than rebuilt ring interface issues. It is almost always a pay for service to have parts machined. I cannot tell how many times I have had parts ruined by a competent machine shop. Problem with them that I have is they machine how they want, not how I or the manufacturer specs.
I went out on a limb to help explain a potential low cost solution. It is not for everyone. Only 1/3 or so of the engines out there are even good candidates, but those capable can save a great deal of expense, and time. Even buying on a parts insurance notion can easily bite you. I greatly respect your opinion to many matters on here. I just wouldn't deter based soely on who generally reads these forums. This technique is actually meant for people with your skill set.
I'm glad you did go out on a limb, this has been an interesting discussion. I can see why you aren't concerned about amount of material taken off - you are primarily glaze breaking - and if the engine is pretty fresh then bore geometry wouldn't be a problem either. It's the question of the hone/glaze breaking residue that bothers me. I see that Flex-hone recommends wiping the bore with a white cloth to check whether the bore has been cleaned sufficiently after honing (cloth should remain white). How well does a solvent soaked towel work - would it pass that test (once the solvent had evaporated from the bore)? Thanks!
I've seen ZD diesels with less than 10 hours run time overheated such that the bores are junk. I've also seen a couple RTV's with 5-7 hours on them, similarly destroyed. Oh and an MX5100 too. I know there were more low hour engines replaced, but I can't think of them all. L3240 I think was another one, actually I'm positive it was a tractor that was similar, and there was another post online on another site about it. Guy didn't check the radiator/screen, ran it hot, shut it off, couldn't figure it out, fired it back up and kept running it until it seized. Repeat several times until it just wouldn't start anymore, then shows up to gripe at me (dealer) because I sold him a pile of junk. Oh, then posts it all over the 'net because Kubota wouldn't warranty an engine, and his insurance wouldn't cover it because it wasn't on his property when failure occurred. Was not KTAC. The one website he was on, he got put in place by someone who knew the rest of the story. Wasn't this site. It's been years ago, when the 3240's (I think that's what it was) first came out.
In the ZD's and RTV's case I talked about above, every one of them decided that it was best to put a head and gasket on it, and return it to service, then at some point, it was back in the shop again for either missing on center cylinder or not running on any of them due to low compression.
Hence, do it right the first time, or don't do it. I've been through all this crap.
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Again, apples to oranges. I expect you know the difference between piston bore seizure and glaze breaking/ring seating.The politics of insurance claims, and cheap owners has no bearing either. Do it right is subjective. Ive thrown many good parts away because of it. Too many
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Yes, it cleans it very well. Cuts right through the cutting oils, and washes the abrasives out. As long as you clean until the rag/paper towel comes out spotless. It is important to oil the cylinders after cleaning. You only have two main ways to clean, soap/degreaser and water or solvent. The washing works fine for a bare engine with machining trash all in it. Solvent wiping the bores is much more practical for this process. I wont take up any more space on this post.
Look for a new post in the future. Ill post pictures of the process.
Pau7220
Well-known member
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L3650 GST, Landpride TL250 FEL w/ Piranha, 6' King Kutter, GM1084R Finish
I will assure you there is no way to remove all the residue from the cylinders after honing.
100’s of times per year I open brake rotor boxes, pull the rotor out of an oil soaked plastic bag, clean off the Wuhan oil with lacquer thinner 2x or 3x, then take it over to the sink with Dawn, ScotchBrite sponge, and warm water…. Then still get grey streaks on the drying cloth.
You may pull it off with the pistons out, with the pistons in….not worth the effort or risk of doing its second time with even more damage.
What are the actual cost savings? A set of rings?
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Not doing it right the first time almost invariably means that it will have to be done again. I'm assuming that some folks value their time/money more than others, hence "subjective"? I don't have much time nor money thus if I have to go into an engine (or transmission or whatever), I tend to do it once. It costs more in this manner but only doing it once means it frees up time/money to do other stuff or to fix other stuff or whatever.
A bit off topic, but related. Years back, my Case 680 CK ate the balance shaft. Pull engine and do full rebuild. New sleeve and piston kit, bearings, seals, gaskets, balance shaft, oil pump, main and rod bolts, valves and guides, valve seats cut. The engine ran OK before it ate the balance shaft. ChecK everything against the Case shop manual. When timing the pump, I find the pump was off about 10 degrees (retarded) from where the injection should have started.
Reassemble the engine and start it. It makes three revolutions and starts. Up the rpm to about 1300 and it won't go above idle. Check pump timing, new filters for leaks, all fine.
Call a well respected diesel injection pump service center and explain everything to a tech there. He explained that the injection pump and injectors worked with a worn engine with lower than spec compression, but now can't overcome cylinder pressure to inject the fuel at any speed above idle. Sounds like bull, but what the hay...I pull the pump and 4 injectors and bring them to the shop.
The tech was nice enough to bring me in the back while he ran his "quick and dirty" pressure test on the pump and injectors. The injectors popped about a hundred pounds low, but all had a bad spray pattern. He showed me the correct spray pattern from another injector that was there as a standard and the difference was night and day.
Testing the injector pump showed it was a few hundred pounds low in output pressure across the board. I told him about the late pump timing and he said that this was done to allow the pump to work when it's output pressure was well below spec.
Rebuilt pump, rebuilt injectors, $1200 later I put everything in and the loader was a new animal. NO choking on the exhaust fumes, idle and governed speed right on the money.
I suspect that the injection pump has low output pressure and the injectors are in need or rebuild or replacement.
I hope all works out for you.
Reassemble the engine and start it. It makes three revolutions and starts. Up the rpm to about 1300 and it won't go above idle. Check pump timing, new filters for leaks, all fine.
Call a well respected diesel injection pump service center and explain everything to a tech there. He explained that the injection pump and injectors worked with a worn engine with lower than spec compression, but now can't overcome cylinder pressure to inject the fuel at any speed above idle. Sounds like bull, but what the hay...I pull the pump and 4 injectors and bring them to the shop.
The tech was nice enough to bring me in the back while he ran his "quick and dirty" pressure test on the pump and injectors. The injectors popped about a hundred pounds low, but all had a bad spray pattern. He showed me the correct spray pattern from another injector that was there as a standard and the difference was night and day.
Testing the injector pump showed it was a few hundred pounds low in output pressure across the board. I told him about the late pump timing and he said that this was done to allow the pump to work when it's output pressure was well below spec.
Rebuilt pump, rebuilt injectors, $1200 later I put everything in and the loader was a new animal. NO choking on the exhaust fumes, idle and governed speed right on the money.
I suspect that the injection pump has low output pressure and the injectors are in need or rebuild or replacement.
I hope all works out for you.
grab your depth mic and measure how far in or out of the cylinder the pistons are at true TDC. Compare that to spec. If out of spec pull the pan and piston assemblies and look at the rods. Might be bent. Sometimes it's not obvious. You can also measure the width of the rod bearings. Not the thickness the width. If the uppers are considerably wider than the lowers, that indicates that the rod has seen excessive force on it. When I am into one, and the rod isn't obviously bent, I'll pull a bearing and measure with a caliper. Without a way to measure center-to-center of the rod, measuring the bearing shell width can oftentimes be an indicator.
I've seen things happen. I specifically remember a B series many years ago, came off the crate. Tractor was assembled at the shop. Assembly techs couldn't get it to start (out of fuel...) so they hit it with the starting fluid after dumping a gallon of fuel into the tank. Sure enough it started. Ran on all 3 but would smoke a little once it warmed up. It was sold that way (don't ask why...), then it came back with the owner pretty upset about it. Had 1.9 hours on it. I did compression test, 2 were 450 one was 400. Obviously lower but still within spec. Well you already know if it's low we have to find out why and try to get warranty to cover it. Pulled head, 2 pistons and 2 rods looked great. The one piston came out and the rings and ring lands fell out (broken), the rod looked fine so I tossed a new piston in it and went on. Still lower than normal compression, pulled it back apart and measured the rod bearing. Upper shell was wider than the lower, so I put a rod in it. Immediately compression came back and the owner went on with life, loves his little tractor even after that deal. 2 points to be made. Don't use starting fluid (EVER) on a kubota and (2) assembly techs are often minimum wage employees that don't know as much as they really should. I think that needs to change but at this point I'm out of the kubota business and what changes and what doesn't is out of my control.
I've seen things happen. I specifically remember a B series many years ago, came off the crate. Tractor was assembled at the shop. Assembly techs couldn't get it to start (out of fuel...) so they hit it with the starting fluid after dumping a gallon of fuel into the tank. Sure enough it started. Ran on all 3 but would smoke a little once it warmed up. It was sold that way (don't ask why...), then it came back with the owner pretty upset about it. Had 1.9 hours on it. I did compression test, 2 were 450 one was 400. Obviously lower but still within spec. Well you already know if it's low we have to find out why and try to get warranty to cover it. Pulled head, 2 pistons and 2 rods looked great. The one piston came out and the rings and ring lands fell out (broken), the rod looked fine so I tossed a new piston in it and went on. Still lower than normal compression, pulled it back apart and measured the rod bearing. Upper shell was wider than the lower, so I put a rod in it. Immediately compression came back and the owner went on with life, loves his little tractor even after that deal. 2 points to be made. Don't use starting fluid (EVER) on a kubota and (2) assembly techs are often minimum wage employees that don't know as much as they really should. I think that needs to change but at this point I'm out of the kubota business and what changes and what doesn't is out of my control.