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reverb Offline OP
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Hello; I stumbled upon 2 videos of engines assembly. One is an small factory with persons instead of robots in the lines; working with small 70cc engines (bikes); the other is the modern BMW plant, with many robots and not so many persons in the assembly lines working on big and racing engines.
In both cases the assembly is done with oil; not with assembly lube and not "dry"
In the case of the 70cc the guy put oil on top of the piston (and rings) and then put over the cylinder- With the BMW he uses oil on the jugs of a 1000RR then insert the rod with the pistons and rings...The video mentions that they use the same oil as the engine will have due to homogeneity
I understand that with these modern engines the honing is done with finer grits and the rings may be are chromed, but for sure are not like the old Brits with iron rings; however, may be the small 70cc use iron rings; I do not know but both engines have different goals and both have oil on the jugs...

-By the way; no threads locker in the rods bolts with the 1000RR or the 70cc in the other factory. No stretch gauges for the rods bolts too.

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In your shop the engine will be started & run the instant you have finished
For a production line engine that might sit for anything up to 2 years before it gets run enough to fully lube the engine thus ruest prevention is the no 1 priority
Horses for courses not right or wrong
Most small engines ( ie mowers & the like ) are started on the end of the production line with no oil, just the lube used during assembly.
Engine is powered by a gas mix fed into the carb throat.
Fires and runs for a dew seconds then it is crate it up & ship.
Does not fire & it is off to mechanical rectification
Would not recommend doing this either


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I can't say about the small engine, but modern BMWs use chrome rings and nikasil lined cylinders. They take forever to break in anyway.
As I understand it, modern oils are too good to break in old iron rings in iron cylinder liners, they don't allow enough contact between the rings and the cylinder wall.
Feel free to use as much oil as you wish, just use cheap, non-detergent oil on the rings.


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Was happily ignorant on the dry assembly topic for years. Never have had a problem with oil and will continue. Starting with my 1st Briggs&Stratton go cart. To each his own I guess. 🥴

Last edited by KC in S.B.; 11/11/22 2:14 pm.

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DOPE
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i start up a fresh build with four (4) drops of oil, one on each piston skirt.

is that dry?

theres more than one way to skin a cat

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Far as I am told by those who work on modern engines, top rings may be chrome plated...But not on grey cast iron...Ring material is steel or nodular iron and might be nitrided...
I use minimal oil like Kevin...may a few drops more, lol


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its a technique i read about years ago in a motorcycle magazine.

my machines make good compression, and i dont have scuffing issues. but that was long ago and maybe metallurgy is different now. i would tend to do what the piston and ring mamufacturer says to do witheir stuff.

this was also from the time when we were all told to scotchbrite the top coats off our rod bearings, and that was crazy

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reverb Offline OP
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Well, in the other side of that many years ago I assembled my 500cc with oil on the pistons and rings and never smoked. I used iron car rings. Made in UK I think.
Of course, many things that appeared in the USA hot rod magazines etc seem good for the builder but the factories (Euro and Japan ones) seem to go on other directions
Regarding the rod bearings is accepted or was accepted that you can sand it or polish a bit (only in the part where you perceive a shadow mark on the new bearing of course; after you torque the bolts but the rod is not spin freely) with steel wool (thinner than a 2500 grit sandpaper) then polish paste to seat properly the rod on the crank.


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