Interesting thread…and interesting techniques… and Each to His Own….
Here’s my opinion on such repairs and observations on THIS one:
Kubotafreak: Fine workmanship as far as your work goes. I mean that…even tho’ I wouldn’t necessarily agree with honing cylinders to improve compressions.
When low compressions are found…the next thing to do, IMO, is to perform a “DIFFERENTIAL” compression-test. This may go by other names…but it’s basically placing a piston on TDC and then injecting air into the cylinder via the spark-plug port or injector port….. and listening for any escaping air.
Escaping air (Hissing) at the intakes is a leaking intake valve—- Hissing at the exhaust pipe is a leaking exhaust valve—- and hissing at the oil-filler-cap is a piston/ring leaking into the crankcase.
If a valve is leaking …it’s a valve job.
If it’s a piston/ring….it’s a bottom-end job. It is NEVER a “cylinder-honing job” with the piston in-situ… alone.
Cylinder walls are honed into a “cross-hatch” pattern for ONE PURPOSE: To Quickly Seat piston Rings. I hope it’s obvious this would be on a NEW or REBUILT engine.
[ It’s my opinion that de-glazing cylinder walls by honing intending to improve compressions is an “Exercise in Futility!” …unless New Rings are also installed.]
Cylinder-walls become glazed because rings did not properly “seat”. Oil by-passes the rings into the upper cylinder and burn into the walls and sometimes contaminate valve train. This can be due to several issues: Obviously failed pistons/rings… but, …in new engines, Primarily Improper Break-In of new engines, …possibly attributed to use of synthetics and “snake-oils” during break-in… and/or improper operations and lack of speed-variation during break-in. Cylinders can glaze if engines pass too much oil via leaking valve-stem-seals also…but the PRIMARY reason is improper break-in (which can include “baby-ing” a new engine. A new engine should experience the full-range of operations during break-in. (Kubota is wrong IMO to suggest that “full throttle” operations should be avoided in early hours of operation. I believe ALL regimes of operation should be experienced for proper break-in.… only avoid full-throttle/hard-work for “extended periods” for the early hours. IMO)
With the above opinion in-mind…there is no reason IMO to ever hone a cylinder with a piston “in-situ”. While the grease-dam Kubotafreak uses is imaginative…it is not a good method IMO because grease will attract the abrasive and the subsequent WD40 will only wash it down into the piston/ring/cyl-wall interface….but that is a subjective matter and involves individual technique…and so he might defend it… I’ll just reiterate that the entire process of honing with a piston still in the bore is a bad idea and no reason for such process is valid. None.
Why? Because cylinder cross-hatch-honing is entirely for the purpose of Seating RINGS… and it does that by MATING the ring-to-cyl-wall interface…primarily by CUTTING the minute cross-hatches and ring-surfaces which become “polished” with each other.
RE-honing an engine somewhere thru it’s operating life (after break-in) at BEST only adds unnecessary wear to rings and cylinders by wearing-away important surfaces…. as already said…”at BEST”. It will not “save” anything..it’s only a waste.…and a hazard to the engine. IMO
The old-timers’ comments/opinion about an oily-rag-test of the cylinder wall is just another interesting but useless process. Cylinder walls that have been honed should be honed using Stoddard or “safety” solvent…Never oil, ATF, or any other lubricant. Solvent will continuously wash-away the “fines” of metal and abrasives from the stones and walls. Oil will “burn” or “coke” and embed into the walls and that is what the old-timer demonstrated…his only advice-failure was in allowing oil to be used during honing.
(The technique I use when honing cylinders is to use a container of solvent resting above the engine along with a siphon blow-gun resting on top of the cylinder with it’s pick-up in the solvent. A short blast of the gun will start the siphon…which will continuously flow solvent into/onto the hone as it cuts the cross-hatch….and washes the cyl-walls immediately and keeps them clean.)
From the pics, it looks like the pistons/rings have failed to control oil…which has glazed the cylinder walls and contaminated the valve-stems. A differential compression-test would have revealed this defect and all this wasted work accomplished so-far could have been saved.
I had this opinion before reading to the end…. but just saying that probably won’t convince a reader that I didn’t come up with this until after Kubotafreak revealed the failed piston…. but it is true.
Summary: Honing with a piston in-place to de-glaze a cylinder is a false-hope of curing the real problem…unless you are willing to accept the fact that you are about to re-seat piston-rings and deliberately remove ring and cyl-wall material… falsely creating the same results as many hours of engine operations. It may fool a potential buyer of used equipment…but it’s not a ”proper repair” for longevity.
Hope this helps.
Here’s my opinion on such repairs and observations on THIS one:
Kubotafreak: Fine workmanship as far as your work goes. I mean that…even tho’ I wouldn’t necessarily agree with honing cylinders to improve compressions.
When low compressions are found…the next thing to do, IMO, is to perform a “DIFFERENTIAL” compression-test. This may go by other names…but it’s basically placing a piston on TDC and then injecting air into the cylinder via the spark-plug port or injector port….. and listening for any escaping air.
Escaping air (Hissing) at the intakes is a leaking intake valve—- Hissing at the exhaust pipe is a leaking exhaust valve—- and hissing at the oil-filler-cap is a piston/ring leaking into the crankcase.
If a valve is leaking …it’s a valve job.
If it’s a piston/ring….it’s a bottom-end job. It is NEVER a “cylinder-honing job” with the piston in-situ… alone.
Cylinder walls are honed into a “cross-hatch” pattern for ONE PURPOSE: To Quickly Seat piston Rings. I hope it’s obvious this would be on a NEW or REBUILT engine.
[ It’s my opinion that de-glazing cylinder walls by honing intending to improve compressions is an “Exercise in Futility!” …unless New Rings are also installed.]
Cylinder-walls become glazed because rings did not properly “seat”. Oil by-passes the rings into the upper cylinder and burn into the walls and sometimes contaminate valve train. This can be due to several issues: Obviously failed pistons/rings… but, …in new engines, Primarily Improper Break-In of new engines, …possibly attributed to use of synthetics and “snake-oils” during break-in… and/or improper operations and lack of speed-variation during break-in. Cylinders can glaze if engines pass too much oil via leaking valve-stem-seals also…but the PRIMARY reason is improper break-in (which can include “baby-ing” a new engine. A new engine should experience the full-range of operations during break-in. (Kubota is wrong IMO to suggest that “full throttle” operations should be avoided in early hours of operation. I believe ALL regimes of operation should be experienced for proper break-in.… only avoid full-throttle/hard-work for “extended periods” for the early hours. IMO)
With the above opinion in-mind…there is no reason IMO to ever hone a cylinder with a piston “in-situ”. While the grease-dam Kubotafreak uses is imaginative…it is not a good method IMO because grease will attract the abrasive and the subsequent WD40 will only wash it down into the piston/ring/cyl-wall interface….but that is a subjective matter and involves individual technique…and so he might defend it… I’ll just reiterate that the entire process of honing with a piston still in the bore is a bad idea and no reason for such process is valid. None.
Why? Because cylinder cross-hatch-honing is entirely for the purpose of Seating RINGS… and it does that by MATING the ring-to-cyl-wall interface…primarily by CUTTING the minute cross-hatches and ring-surfaces which become “polished” with each other.
RE-honing an engine somewhere thru it’s operating life (after break-in) at BEST only adds unnecessary wear to rings and cylinders by wearing-away important surfaces…. as already said…”at BEST”. It will not “save” anything..it’s only a waste.…and a hazard to the engine. IMO
The old-timers’ comments/opinion about an oily-rag-test of the cylinder wall is just another interesting but useless process. Cylinder walls that have been honed should be honed using Stoddard or “safety” solvent…Never oil, ATF, or any other lubricant. Solvent will continuously wash-away the “fines” of metal and abrasives from the stones and walls. Oil will “burn” or “coke” and embed into the walls and that is what the old-timer demonstrated…his only advice-failure was in allowing oil to be used during honing.
(The technique I use when honing cylinders is to use a container of solvent resting above the engine along with a siphon blow-gun resting on top of the cylinder with it’s pick-up in the solvent. A short blast of the gun will start the siphon…which will continuously flow solvent into/onto the hone as it cuts the cross-hatch….and washes the cyl-walls immediately and keeps them clean.)
From the pics, it looks like the pistons/rings have failed to control oil…which has glazed the cylinder walls and contaminated the valve-stems. A differential compression-test would have revealed this defect and all this wasted work accomplished so-far could have been saved.
I had this opinion before reading to the end…. but just saying that probably won’t convince a reader that I didn’t come up with this until after Kubotafreak revealed the failed piston…. but it is true.
Summary: Honing with a piston in-place to de-glaze a cylinder is a false-hope of curing the real problem…unless you are willing to accept the fact that you are about to re-seat piston-rings and deliberately remove ring and cyl-wall material… falsely creating the same results as many hours of engine operations. It may fool a potential buyer of used equipment…but it’s not a ”proper repair” for longevity.
Hope this helps.
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