Triumphrat

lovecuba

Running engines in. Bit of a misnomer really as against bedding the engine in. The latter is the most important. Research has shown that piston rings in particular are bedded in within the first 18 full revolutions of the running engine (cast iron compression rings) when the revolutions are high 2000-3000. At this time new followers and freshly ground (or new) camshaft lobes benefit greatly from the high rev scenario when coated with the correct cam lube. So, bedding in is done on the stand(still) with the engine at the above revs. DO NOT ALLOW THE ENGINE TO IDLE!
Running in is when the bike is actually ridden, given that the high spots on rings and cylinder walls have been removed it is time for some aggresiveness to complete the whole process of making an extra good seal between rings and bores. If the rings have been gapped correctly then there is very little chance of nipping a piston skirt or seizure.
Even though running two oil filters I shall change the running in oil at 50 miles and again at 100 whereupon my decided brand of 20/50 motorcycle oil will be added.

JohnA

You could get through more than 18 revolutions just trying to start the thing, if anything's amiss!

What should one do if that happens? Whip the top end off and fit another set of new rings?!

Seriously though, I'd agree with keeping revs between 2000 and 3000 on first start-up, until warm anyway (though I wouldn't call such revs high). I don't think I'd ever start a cold bike and immediately let it idle.

I think what the differences in opinion exposed by this thread show is that breaking-in//bedding-in/running-in methods really aren't that critical - they will all work well enough provided a reasonable degree of common sense is used.

Old Cafe Racer

Just a few observations from my 40 odd years of assembling engines and why I oil things first.
I'll never assemble a piston/ring/cylinder assembly dry ever again.
The only times I've done that, when pulled down again for inspection the pistons and bores were scored.
I also found that on dry bores the rings don't rotate initially as designed due to increased friction and heat which is normally carried away /prevented by the oil film.
Reason is quite fundamental, it doesn't matter how clean you think it all is, when it's assembled there will always be some microscopic contamination between bore and piston.
Second, soon as the engine fires, small abrasive bits of the rings and cylinder walls come away as the two rough surfaces are forced together and considerably add to the dry debris accumulating between the piston skirt and cylinder wall and without the thin oil barrier to wrap up and wash away this stuff scoring will be the result in the first few seconds of the engines life.
So I very lightly smear the bore, piston and rings with running in oil on assembly and in spite of opinion to the contrary, obtain a full circumferential seal on all three rings in a very short time.
The oil also helps gain more initial compression which forces the rings harder against the cylinder walls in the first few revs of the engines life seating the rings even quicker.
You pays your money and takes your pick but I like to think I've done my homework and taken as many factors, as well as experience into consideration.

davy

lovecuba

Hard to kick over when it is running. And, heat is an important part of the process.

The 18 revolution business is well known in engine reconditioning circles and was explained to me by a very professional and competent engineer, who I might add advises to use an absolute minimum of lubricant on the bores, rings when assembling. In fact he advises a dab of oil on each piston skirt, washing the cylinders in hot soapy water (to remove any oil residue) clean pistons and rings. Different strokes for different folks?

Old Cafe Racer

18 revs takes around half a second at around 2500 rpm.
I'm having trouble with the concept.

.

lovecuba

So was I! Will garner more from Him soon and perhaps be able to explain it in a more rational and understanding way (good for me to), He is timing the camshafts and expect a call soon.

Mr.Pete

If the pistons sieze,there could be 3 causes:

*Not enough clearance (no amount of gentle running in will fix that).

*Minimum piston skirt clearance (still OK for a bedded engine),and too much blowby fom new rings heating the piston.This won't happen if you close the throttle every few seconds to allow the piston to cool.Closing the throttle for a few seconds also draws oil up to the rings,to wash away any small metal particles.Constant low throttle at the same speed doesn't do this,and the pistons run hotter.

*Not enough rpm with throttle open,detonation,and the pistons are about to melt.This mainly happens when people are "taking it easy" and keeping rpm down.It's not likely to happen at 4000 + rpm.

Scuffing/scratching of pistons can happen if cylinders aren't carefully scrubbed with hot soapy water after honing.It can also happen with no air filters.Even "dry" assembly is done with a drop of oil on front and rear of each piston skirt.The cylinder still has some oil,ATF or WD-40;all the excess has been wiped off as much as possible.

High detergent/dispersant oils are likely to cause cylinder glazing if the engine isn't loaded enough during running in.We have more detergent than in the good old days.

Bore glazing or not,the rings need to be seated and fit well.Nothing else in the engine reallly needs to be run in.Until the rings are bedded,you get leakage past the rings.It heats the rings and the piston.The rings are less likely to leak when they are loaded and pushed against the cylinder by gas pressure,but it will still happen at first.

Nobody is saying go out and thrash a new engine at continuous high horspower and high speed.Average power,over any 5 or 10 second period,should still be low at first.1/2 revs with the throttle closed 1/2 the time (engine fully loaded the other 1/2 of the time),is still only an average of 1/4 of your maximum potential power output.It causes no more harm (and a lot less),than running at constant 1/4 throttle.If you're trying to wear out throttle cables without excessive speed,you probably have it right.You won't be using top gear unless you get up to highway speeds.

The high load/no load method of bedding in does work.It works better than running at constant light-to-medium load and cooking the rings with blowby.It makes more power when the engine is bedded,and gives better engine life.I've been doing this since the '70s.I've been using "dry" assembly and even lapping-in rings,since the mid '80s.Lapped rings give less blowby,and it stays that way.
Motoman does it slghtly different,but not much.Results are good.Google-search "mototuneusa".


I don't agree with the 18 revolutions bed-in.It takes nearly 40 revolutions with Bon-Ami as abrasive to get cast iron rings partly seated (there will be a continuous line of contact around the ring).Most people would say at least 50 miles of on/off,on/off to get the same effect without lapping on a petrol engine.

Morris the Cat

That information shows up in the 'Owners' manual- talks about snapping the throttle shut to do as you said.

Mine was second hand bought- no owners manual!

"Freeing the Clutch" was also mentioned, sure wish I had that book!

__________________

Morris of Main Street

DAVE M

owners manuals are available online as pdf's and as repros.

My original 79 one was so knackered that I bought a replacement from (I think) LP Williams. Someone moaned on here about the poor repro quality of their copy but mine looked like the original.

We forget what a typical 70's office document looked like. Word/DTP has turned us all into "graphic designers". The current standard repop owners manuals is equal to the original with a not very good photo inside. That's why Triumph stuck with line drawings as they were cheaper to reproduce then.

JohnA

Thanks Pete for this clarification. It seemed as if people were recommending virtual thrashing from first startup. The 'snap the throttle shut to force oil up the bores' advice, and the 'don't stick to a constant speed, instead vary the engine speed and load as much as possible' advice, and the 'don't lug the engine - this is even more important than avoiding using fast engine speeds' advice is all very well established. I remember reading all these tips in a pre-war book called "The Unapproachable Norton: an owners guide", published some time around 1936.

What's new seems to be the advice that oiling of new bores & pistons should be kept to the bare minumum. This goes against the way I learned (which was to oil everything generously). As I've said above, I have never experienced any problems after many thousands of miles in several cases, having rebuilt engines following this method. If the 'oil minimally' approach works - as I have no doubt it does if so many eminent mechanics say so - maybe I'll give this a try next time. No way am I zooming up the road a matter of seconds after first startup though!