Is 40 weight oil good enough to prep 50mm BBK?

[scootnewb]

When installing the BBK, is coating the new piston and cylinder with 10W40 acceptable or do I need some special lube?

Thanks

[KSR Moto]

I use 2 stroke oil, but you can use pretty much any engine oil just to provide that initial lubrication, just make sure that you apply thin coat of oil on everything,you should never assemble engine dry

[scootnewb]

Thanks.


I re-assembled the stock top end after finding the BBK I ordered came with the wrong piston. I coated the jug and piston with motor oil and it was good. After that fiasco, I started reading up and some claimed using special lube was necessary. 

[KSR Moto]

Apr 25, 2018 16:27:53 GMT -5 scootnewb said:

Thanks.


I re-assembled the stock top end after finding the BBK I ordered came with the wrong piston. I coated the jug and piston with motor oil and it was good. After that fiasco, I started reading up and some claimed using special lube was necessary. 

I never used any kind of special lubes just for assembling the engine, usually 2 stroke oil or oil that you will use in your engine is more than good

[jmkjr72]

Cams are the on,y place that need anything special
I us Dino for assembly not synth

[scootnewb]

Oh? what should I put on the cam? Put it all over the cam?

[ThaiGyro]

I am enjoying this! As an old timer, I have seen more methods than most of you have birthdays. Truth is as told, use something oil based, preferably, non-synthetic. In the US, we used "Marvel Mystery Oil" quite often for assembly. Thin and easily wiped of excess. Nothing wrong at all with using the lube you use as premix or pump. Makes some sense!

The thing is, you don't need much, but coat all contact surfaces BEFORE assembly. I am a WD-40 hater, never use for assembly. My view, (as an oil industry engineer) is that WD-40 is designed very well...to make money! You are buying super light gases that evaporate uber fast. Cheap? Yes. Valuable? Nope. We are lucky here to still have MOS2 oil. (molybdenum di-sifide) It is my first choice. Gun manufacturers use it for assembly and protections. US put it on the EPA list. Bummer.

Regarding cams. Super old method for break-in was to use non-detergent 30 weight motor oil. Todays "break-in oils" are just that. Maybe 40 weight.

If you have done any cam grinding or installing a new cam there are cautions: First, some ship pre-lapped, meaning mating surfaces are smooth like a babies butt. If the manufacturer doesn't say it was lapped, you should do it. We rarely used oil for that. Some buy lapping compound. Too much waste for me. We used toothpaste! Super fine grit, polishing compound. I put a cam on the lathe or a welding turntable, start it rotating, first using super fine emery cloth, then use an electric toothbrush with your favorite flavor. Wipe clean, oil coat and install! Bad ass, no heat, no fuss, no money! The emery should follow the proper rotation direction, the toothpaste is for final polish.

[GrumpyUnk]

I read that 'performance' cams, with high lift, long duration and stronger than factory valve springs, needed 'cam assembly lube' and 'need to run for 30 minutes' upon first start of the engine.
I assume(yeah, I know) that this really only applies to cams for modded car & truck engines. Those that are equipped with much stronger valve springs to handle high rpm use without valve float.
I don't think anything special is needed on the gy6 of 139qmb valve lobes for break in. There just is not enough tension on the cam followers rubbing on the lobes to need it. I can compress the valve springs using a couple thumbs(I borrow from the neighbor... ha!), which, to me, indicates there's not a lot of shear going on between the lobe and follower. IOW, they are low friction designs as there just isn't enough force to need anything special.
I realize that "ZDDP" has been removed from auto lubes of the SN API variety(I think SN, but ...), which is not good, reportedly, for flat-tappet lifters or cam followers. I read that it likely doesn't matter that much for most 'civilian'(factory) engines as the valve spring pressure is too low to need a lot of protection. I report, you decide. Go to bobistheoilguy for multiple discussions.
I am running diesel spec oil in the herd. It still contains a bit of ZDDP, again, from readings, as I do not do chemical analysis of lube oil additive packages. I use Wally World 15W40. I figure if it can pass the API ratings test, it must be ok. My understanding is that the lubes are a Marathon Oil Co of Findlay OH product. or Valvoline. Don't really care.
When doing a BBK, I'll use regular motor oil. But I am very liberal in its application. I want it lubed for easy insertion of the piston into the cylinder, rings sliding on the cylinder bottom 'ramp', and good cylinder wall & piston lubrication for startup until the 'splash' effect gets going. These engines have ball bearings on the crankshaft, and they require different lubrication than 'plain bearings' used in larger engines, and some OPE engines(outdoor power equipment), which may have some ball, some plain bearins, and be either splash, partial pressure, or full pressure lubricated. Ball bearings roll on the balls in the races. The lube is to carry heat away, and the bearing does NOT depend on oil pressure to force lube between the bearing and the journal as plain bearings do(even gravity fed splash has a smidge of pressure). The lube requirement is so small that the 40:1 and 50:1 2T mixes provide enough lubrication and heat absorption for the ball and needle bearings used. It doesn't take much. If you pay attention, most 2T failures are piston, ring and cylinder wall galling caused by overheating or total lack of lubrication. I suspect the cylinder walls require added oil a lot more than the actual bearings. As long as there is a 'splash' of oil on the cylinder wall, be it the cheapest lube you can buy, most engines will run fine, but their longevity will be improved with clean oil that is changed on a reasonable basis. Lecture off.
tom

[scootnewb]

I finally installed the BBK and used 15w40 to coat everything and before I started it back up, I did an oil change also with 15w40. It started right up.


I got the new Keihin ready to go and I put in a 35 pilot and 98 main. Up from 33 and 85. Today I'll put it in, try tuning it, ride it for a bit then do another oil change. Oh yeah and put the shrouds and rubber ring around the engine.

It started raining after finishing up the install but it sounds ok - no metal clanking sounds but needs a tune up.