TOPIC:

swest wrote: I stand corrected. I just went to my Wiseco chart and it says,
Stock
Top ring.0050"
2nd ring,0055"
Oil rails min. of .010"
"The gap on the second ring should be larger than the top ring end gap, this will help to reduce top ring flutter or lifting."
High performance street/strip, .0045,.0055

Maybe they are using some kind of steel that is formulated to not expand much. I know on my 750 twin, the stock nominal end gap is about .008" - .014" ballpark for piston that has about 3" bore diameter.

What surprised me was that max allowable end gap was .028" (which is almost a spark plug gap) and seemd like it would blow by a lot of gas. But, according to the text, most of the blow by occurs along the length of the ring past the gap in the piston, not the end gap.

650ed wrote:

bountyhunter wrote:

The results are always the same... a dramatic increase in power at all RPMs. In addition, many professional mechanics have disassembled engines that have used this method, to find that the condition of the engine is much better than when the owner's manual break-in method has been used.

Well, somebody is certainly full of themselves. I, and probably 99% of bike owners, used the "owner's manual" method and never had a problem. I personally got about 80k miles on my first set of pistons and rings, had excellent compression and didn't blow a drop of oil so I don't know what else one can expect from rings. I also inspected the cylinder walls at rebuild and they looked good to me. Bored it out .010 and installed the next larger pistons/rings and did the same thing. Perfect compression, zero oil usage again.

Personally, I don't think proper break in is as complicated as some would claim. If it was, a lot more bikes would be spraying oil out the tailpipe.

+1 !!!

I suppose he would consider the following "Break" in method to add plenty of power at all rpm. Ed

Looks like he got what he asked for. GAFAAAA!

Another article:

www.ktm950.info/how/Orange%20Garage/Engi.../engine_breakin.html

We asked four top motorcycle engine builders what they do to ensure peak power output and optimum engine life. Here is a capsulation of their responses:

If the wrong type of oil is used initially, or the break-in is too easy, rings and cylinders will glaze and never seal properly. A fresh cylinder wall needs some medium to high engine loading to get the piston rings to seat properly for good compression, but make sure you don't lug or overheat the engine. Use high quality, low viscosity oil (10W-40 weight), no synthetics, too slippery. If synthetics are used during initial break-in the rings are sure to glaze over.

An engine's initial run should be used to bring oil and coolant (air, oil, and/or water) up to operating temperature only, with little or no load, then shut down and allowed to cool to ambient temperature. Do this in neutral before ever riding it. This is important and quite vital to camshaft longevity. Vary the RPM's between 2500 and 4000 for 15 minutes, After this run the engine needs to completely cool down to ambient temperature.

After a cool down period, start it up again and take the motorcycle for it's first ride.
Cool (but not slippery) conditions are desireable if at all possible.

This time, give the engine light loads at relatively low rpm and stay out of top gear to warm up the engine completely. Proper warming up of the engine is critical. The clearance between the pistons and the cylinder bore is very tight until they are completely warmed up. The piston expands faster than the cylinder and can scuff (metal to metal contact) inside the bores if the load isn't kept low until expansion equalizes. Lugging the engine is more detrimental than high rpm. Another key is to constantly vary engine load during the entire break-in period. A constant load is not ideal for breaking in.


Now use 4-5 short bursts of acceleration at 1/2 throttle to 50% of redline, followed by deceleration against engine compression (no brakes) to help seat the rings. This deceleration against engine compression is a vital part of the break-in process, as it draws oil up onto the cylinder walls cooling the rings and washing the loose metal particles away. Warning: Make sure no one is behind you when you do this. Use the lower gears. High speeds are not necessary, nor desired. Keep an eye on engine temperature and don't allow your engine to overheat. Turn it off and allow it to cool down if necessary.

Next, providing all is well with the engine and it is warmed up (not overheating), do 4-5 more short bursts of acceleration at 3/4 throttle to 75% of redline following each burst with deceleration against engine compression.

Finally, make 4-5 more runs at full throttle all of the way to redline, again followed by deceleration against engine compression.

Then head back to the garage, and while the engine is still warm drain the oil, clean any screens, and change the filter.

I personally don't see any reason to do WOT runs to redline on a brand new engine..... but it's user's choice.

This article also contains the myth about how syns won't let the engine break in..... some of the highest performance cars on earth come from the factory with syn oil.

From an aircraft mechanic:

When the engine is operating, a force known as Break Mean Effective Pressure or B.M.E.P is generated within the combustion chamber. B.M.E.P. is the resultant force produced from the controlled burning of the fuel air mixture that the engine runs on. The higher the power setting the engine is running at, the higher the B.M.E.P. is and conversely as the power setting is lowered the B.M.E.P. becomes less.

B.M.E.P is an important part of the break in process. When the engine is running, B.M.E.P. is present in the cylinder behind the piston rings and it's force pushes the piston ring outward against the coarse honed cylinder wall. The higher the B.M.E.P, the harder the piston ring is pushed against the wall. The surface temperature at the piston ring face and cylinder wall interface will be greater with high B.M.E.P. than with low B.M.E.P. This is because we are pushing the ring harder against the rough cylinder wall surface causing high amounts of friction and thus heat. The primary deterrent of break in is this heat. Allowing to much heat to build up at the ring to cylinder wall interface will cause the lubricating oil that is present to break down and glaze the cylinder wall surface. This glaze will prevent any further seating of the piston rings. If glazing is allowed to happen break in will never occur. We must achieve a happy medium where we are pushing on the ring hard enough to wear it in but not hard enough to generate enough heat to cause glazing.

The normal prescribed flight procedure after ring replacement is to keep ground running to a minimum, take off at full power and reduce to climb power at the first available safe altitude, all while keeping the climb angle flat and the climb airspeed higher to promote the best cooling possible. At cruise altitude we should use 65% to 75% power and run the engine richer then normal. At all times we are to remember that heat is the greatest enemy of engine break in, we should try to maintain all engine temperatures in the green, well away from the top of the green arc or red line. This means step climbing the aircraft if necessary, operating with the cowl flaps open or in trail position during cruise flight and being generous with the fuel allocation for the engine. We should not run the engine above 75% power in cruise flight because the B.M.E.P is too great and the likelihood of glazing increases.

This article gives both the traditional and "instant" break in methods......

www.motorcycleextremist.com/Motorcycle-E...-the-Right-Way!.html

Race engines are typically broken in on the dyno running high load after the warm up period.

I worked at an auto assembly plant and got to spend time at the engine dyno rooms. The engines were started from cold and immediately reved up under load. After the engines were installed on the line, they are started up with the car/truck on a chassis dyno. After a brief series of tests the vehicles are brought up to something like 80 mph at HIGH throttle load. Not exactly a gentle break in period.

Piston aircraft engines are also broken in under load. Not the type of load as detailed in that mototune procedure, but people that are interested might want to read this...www.tcmlink.com/visitors/carenfeed/brkin.pdf

"During ring seating, the basic purpose is to establish metal-to-metal contact between the piston ring face and the cylinder barrel. In order for this process to take place, the rings must breach the lubricating film of oil on the cylinder wall. As the rings begin to seat, the ring-to-cylinder wall surface area increases and it becomes harder for the rings to breach the protective film of oil. You can aid in this process by keeping the combustion chamber gas pressures at high levels during the early stages of break-in. The higher combustion gas pressures, as controlled by throttle position, force the piston rings to expand against the cylinder walls, breaching the protective film of oil and allowing the slight wear that we are trying to achieve.

During initial break-in it is not uncommon to have cylinder head temperatures above the normal range for several minutes. This elevated temperature is an indication that initial ring seating is taking place. As the rings begin to seat to the cylinder walls, the temperatures will drop. This usually occurs over a period of 10 to 20 minutes. Cylinder head temperatures can remain slightly elevated for several more hours until complete ring seating has been accomplished. Ideally, the rings should seat within the first 10 to 15 hours of engine operation as evidenced by stabilized oil consumption and decreased cylinder head temperatures."

Cleanliness during assembly, correct ring end gap, cylinder hone and the ever important cylinder preparing procedure have everything to do with piston ring break in.... the rest, including all the snake oil remedies ranging from graphite to Granny's Groin Grease are a complete waste of time and can be detrimental to the process... JMO

..

I've read that ktm950 link before, and have my doubts about it.

I've read that drag racers seat rings with just a few WOT passes, but then they aren't expecting 80k out their motors.

I know the ring gap service limit kawasaki spec is a bit conservative, 1 thou over makes no difference on the dyno I'm told.

That you tube link I've seen before- what sort of muppet pegs a motor into the red in nuetral? quite a few actually - a few years ago at UK Hell's Angels bulldog bash meet it just got a bit boring, every meathead and his were dog popping their bikes off the rev limiter. I have heard one go pop too, followed by much laughter and applause...potentially dangerous too like a hand grenade going off between your legs.

It appears most are in agreement here. I will add just one more thing. When I replaced a broken piston back in my terrible twenties, I had no hone, come to think of it, I barely had the tools to take it apart. I reused the rings and got poor performance off the bat. It was suggested I drain the oil and put in ATF and ride it for a few miles. I did, white smoke coming out the pipe. Afraid of getting a ticket, I put back in my oil ( Castrol GTX 20/50). I ran it until my next tear down. No glazing, scores or anything. It worked. ATF has high detergent in it and low viscosity so those old rings seated at least well enough to run. I rode the piss out of it.
Steve

some of the highest performance cars on earth come from the factory with syn oil.

You are correct most high performance cars and motorcycles today are shipped with synthetic oils. The problem is we are not dealing NEW engines here. The manufacturing process has changed over the last 40 years. engines now days leave the factory without needing any break in at all. So those engines can use synthetic oils.
I seriously doubt anyone building an engine in our garage can match the machining process that goes into new engines. Speaking from only my own experience using synthetics for ring break in will end up with an engine that burns oil and have low compression I have seen it over and over and over and over again. Even modern conventional oils sometimes will not allow rings to seat. I break in all my engines with a stash of NOS 30 weight car oil I hoarded back in the late 70's and early 80's. That oil works great for break in. I don't know what I am going to do when I run out of it. DO NOT USE synthetic oils for initial break in.

Very interesting & informative thread! THIS kinda discourse is what keeps me loitering around here! LOL!

baldy110 wrote:

some of the highest performance cars on earth come from the factory with syn oil.

You are correct most high performance cars and motorcycles today are shipped with synthetic oils. The problem is we are not dealing NEW engines here. The manufacturing process has changed over the last 40 years. engines now days leave the factory without needing any break in at all. So those engines can use synthetic oils.
I seriously doubt anyone building an engine in our garage can match the machining process that goes into new engines. Speaking from only my own experience using synthetics for ring break in will end up with an engine that burns oil and have low compression I have seen it over and over and over and over again. Even modern conventional oils sometimes will not allow rings to seat. I break in all my engines with a stash of NOS 30 weight car oil I hoarded back in the late 70's and early 80's. That oil works great for break in. I don't know what I am going to do when I run out of it. DO NOT USE synthetic oils for initial break in.

Not to thread drift, but about 99% of the oil sold in the USA labeled "synthetic" is actually mineral oil that has been sent through a process called hydrocracking so I assume you mean not to use "synthetics" that actually use a man made base stock.