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Cylinder Bore-Rings-Honing Information
Information below is to help our customers - Motoxparts like to make sure our customers get the correct advice, so they get the best performance and life from their products purchased from Motoxparts - this keeps everyone happy! And off course the customers comeback which is good for us. Motoxparts see it not just as business, we like to have a good friendly relationship with our customers.
You can normally get away without honing a bore on a 2-stoke, (as long as the bore in good condition and the clearance is correct) as 2-stroke do not have oil rings, so if the rings do not break-in correctly the engine will not use a lot of oil, unlike a 4-stroke would if not honed. But when fitting rings to any un-honed bore, the ring life will be reduced and the engine will never achieve full power output as the ring-bore seal will never be as good if the cylinder-bore was honed. You may say this is not true, it has been proven hundreds of times, every ring manufacture states cylinder- bore must be hone correctly for rings to wok correctly, and of course why is every new motorbike cylinder-bore honed from new - I wonder?
All 4-stroke bore must be hone when installing a new set of rings, this is a absolute must, no if or maybe. If this is not done the engine will burn oil, the ring to cylinder wall will get compression blow-by (compression leaking past the rings), blow-by can courses all sorts of problems, high oil burning, blow oil out of the crankcase breather, burning oil from the piston-bore casing a seizure, leaking engine oil seals, low engine power. What is the point of fitting a new part when you want to achieve a good result, by missing out the most important part and for only a few dollars more it can be done right.
Why so important
The first few miles of a new piston-rings life has a major impact on how strongly that engine will perform, how much oil it will consume and how long it will last. The main purpose of correct cylinder-bore preparation is to have a outcome that the rings will have a good seal to the cylinder-bore walls. We are talking about the physical mating of the engine's piston rings to it's corresponding cylinder wall. That is, we want to physically mate new piston rings to the cylinder wall until a good tight compatible seal between the two is achieved.
Proper engine break in will produce an engine that achieves maximum power output with the least amount of oil consumption due to the fact that the piston rings have seated properly to the cylinder wall. When the piston rings are broken in or seated, they do not allow combustion gases to escape the combustion chamber past the piston rings into the crankcase section of the engine. This lack of "blow-by" keeps your engine running cleaner and cooler by preventing hot combustion gases and by-products from entering the crankcase section of the engine. Excessive "blow-by" will cause the crankcase section of the engine to become pressurized and contaminated with combustion gases, which in turn will force normal oil vapors out of the engine's breather, causing the engine to consume excessive amounts of oil.
In addition to sealing combustion gases in the combustion chamber, piston rings must also manage the amount of oil present on the cylinder walls for lubrication. If the rings do not seat properly, they cannot perform this function and will allow excessive amounts of oil to accumulate on the cylinder wall surfaces. This oil is burned each and every time the cylinder fires. The burning of this oil, coupled with "blow-by" induced engine breathing, are reasons that an engine that hasn't been broken in will consume more than its share of oil.Proper engine break in will produce an engine that achieves maximum power output with the least amount of oil consumption due to the fact that the piston rings have seated properly to the cylinder wall. When the piston rings are broken in or seated, they do not allow combustion gases to escape the combustion chamber past the piston rings into the crankcase section of the engine. This lack of "blow-by" keeps your engine running cleaner and cooler by preventing hot combustion gases and by-products from entering the crankcase section of the engine. Excessive "blow-by" will cause the crankcase section of the engine to become pressurized and contaminated with combustion gases, which in turn will force normal oil vapors out of the engine's breather, causing the engine to consume excessive amounts of oil.
In addition to sealing combustion gases in the combustion chamber, piston rings must also manage the amount of oil present on the cylinder walls for lubrication. If the rings do not seat properly, they cannot perform this function and will allow excessive amounts of oil to accumulate on the cylinder wall surfaces. This oil is burned each and every time the cylinder fires. The burning of this oil, coupled with "blow-by" induced engine breathing, are reasons that an engine that hasn't been broken in will consume more than its share of oil.
We hear this lot - I can still see hone marks in the bore so I thought I could just get away without honing it. This is the worst mistake that seem to be made, and just because you can see the old hone marks means nothing.
Even if you can still see the worn hone makes after 5-10 hours work you still must hone the bore every time new rings are installed. Once the raised hone points are rubbed off, a new hone job is needed.
Honing a bore creates very light raisers on the bores surface, these high points in the hone is what makes the ring mate to the bore to create a good seal. Honing attaches like a very light file to make both surfaces smooth and even and to mate, it also protects the rings for contacting the bore during run in.
Honing a bore must be done by a experienced person with good knowlegde of what they are doing on why. This job is for a good engine reconditioner only.
Correct honing of a cylinder bore is not just about jamming a hone in and going up and down. This is very hard for the average person and most mechanics to understand this as well, as they are never been taught how important this job is or even what honing a bore really does, let alone have the correct tools. We do know this as we used to hone cylinder bores correctly every day for mechanics.
Honing the bore correctly should be done by a person with years of experience and good knowledge of this job. By using the correct grade daimond hone, correct hone machine with the correct speed and revolutions, to achieve the correct finish to what type of bore material is being honed. Even using the correct type lubrication during the hone is important.
Below is showing the surface finish, with different crosshatch’s. A professional will normally use surface finish gauge to check the bore finish is correct. No guessing, as guessing only leads to problems.
When a cylinder is new or overhauled the surface of its walls are honed with a diamond hone to produce the correct surface finish that will help wear the piston rings in. This roughing up of the surface is known as "cross-hatching". A cylinder wall that has been properly "cross hatched" has a series of minute peaks and valleys cut into its surface. The face or portion of the piston ring that interfaces with the cross hatched cylinder wall is tapered to allow only a small portion of the ring to contact the honed cylinder wall. When the engine is operated, the tapered portion of the face of the piston ring rubs against the coarse surface of the cylinder wall causing wear on both objects.
Each tiny groove acts as the oil reservoir holding oil up to the top level of the groove where it then spreads over the peak surface. The piston ring must travel up and down over this grooved surface, and must "hydroplane" on the oil film retained by the grooves. Otherwise, the ring would make metal-to-metal contact with the cylinder wall and the cylinder would quickly wear out.
However the ring will only ride on this film of oil if there is sufficient surface area to support the ring on the oil. When the cylinders are freshly honed the peaks are sharp with little surface area. Our goal when seating the rings on new steel cylinders is to flatten out these peaks to give more surface area to support the rings, while leaving the bottom of the groove intact to hold enough oil to keep the surface of the cylinder wet with oil. At the point where the top of the peaks produced by the honing operation become smooth and the tapered portion of the piston ring wears flat break in has occurred.
Some people will state that they never hone a bore on a 2 or 4 stroke – For $30-$40 you will be silly not to have a cylinder-bore honed.
A new cylinder is hone from the factory to make the rings work correctly, why would you not do the same?
Very important after honing the bore must be clean thoroughly in hot soapy water, and then apply a very very thin lay of oil so the surface does not start to rust. Do not use CRC as this can damage the rings if left on when fitting the piston into the bore.
Things you maybe told or read on the internet that is not true
You will hear some people say my engine burnt oil when fitting new rings, so the rings must have been bad, (no such thing as a bad ring set) but to be truthful they did not perform the job correctly. You have been told or read - I do not have to hone the bore - You must if you want a successful outcome (mainly 4-stroke) - this has been proven hundreds of times, every ring manufacture states bores must be honed correctly before installing rings, for the rings to preform correctly, and of course why every new cylinder is honed from new I wonder?
Yes you can hone a plated bore, we get asked the everyday as a shop told them it cannot be honed, well one thing will be true they cannot hone the bore as they would not have the knowledge let alone the correct machine to do the job. Go and see a good engine reconditioner a good one with the correct machine with a diamond hone, will say we do it no problem at all.
And no the plating is not that thin that the cylinder cannot be honed or honing a cylinder will remove all the plating. Cylinder plating is normally .10mm or 004" when a cylinder is hone with the correct hone a diamond hone it will only remove .01mm or .00025" this is barely removing any materiel from a good condition cylinder.
Who should in get to get to prepare cylinder bore correctly?
Never use a ball/bead hone
Ball/bead hones should never be used in bores with ports, as the balls on the hone can clip the plating. What happens is the balls a forced in/out of the 2-strokes ports at speed this can clip the edges of the plating causing big problems down the track. Ball/bead hones are very cheap workers tool and not really that great on any bore. A ball/bead hone is normally used because they cannot use or afford a diamond hone machine which can cost $80,000, and the person doing the job with a ball hone does not understand why a bore is honed.
Lack of engine knowledge is the largest problem for engine related problems in the industry if the cause of a lot of problems. The she will be right attitude or give it ago is normally simply some does not know what they are doing and 90% of the time the outcome will not be good. Please see the right people for the job.
Do not hone plated bores with hones below as the outcome will be a poor hone job and the engine may use oil or smoke