So, I'm on kzrider and these guys keep going on about this ZDDP additive. Is it really necessary to add it to your oil? I'm an engineer so I'm a bit skeptical of all their arguments because I haven't heard one real scientific argument for it. And I see a lot of evidence that adding it to oil is not necessary. The reason they give is that we have flat tappets in our old bikes and the valve springs aren't as stiff in new bikes so they don't need the high antiwear protection. I say they are full of it because valve springs in new engines might have less weight to return to the seat, but they have to do it at much higher speeds. My gut feeling is to go ahead and build my engine with assembly lube, break in on some cheap moto oil just because its cheap, and then run some full synth Motul 7100 once she's broken in. These guys are the same people who use Rotella T in their bikes because it costs $3 a quart so I'm not convinced they're completely sane. Am I out to lunch?

Harry I agree with you on the valve spring and valve weight.But no additive will ever make up for a good oil.My old crew chief has built 100's of race engines over the years.He built one head for me useing busa tappets in a gsxr 1000 head,serious machine work.Any way the seat pressure on these
springs was crazy,like 110 lb give or take.Cams were carpenter 440 cams not sure of the specs but the biggest they offer.The point I am makeing is he recommended the same brake in as you are planning with motul factoryline full syn oil.Funny thing is all the top bikes I know of use the same oil.Even know of some teams sponsored by other brands,guess what they use motul also.I think that a good oil needs no additives.I do know that motul factory line give great clutch life also only way I could ever make it through a race day with a lockup and 1 clutch pack.
Also anyone who knows anything about modern sportbikes will tell you valve spring pressures are at there lowest with ti valves but valvetrain wear is at it's highest.Everyone I know who races a GEN 2 busa switches to the old complete valvetrain or aftermarket.
Hope I did not get off topic but oil is one thing I have experimented with lots.

You didn't get off topic at all, everything you said aligns perfectly with my knowledge of engines and wear characteristics. A good, modern synthetic oil will perform much much better than any old dino crap with random additives put in it by hick racers.

I'm almost done school and I want to work in engine research and development in Germany, so I learn everything I can about engines. It really worried me that all these guys started telling me something that clashed so much with everything I know about this stuff. Some people think that engine technology and lubrication technology is some kind of black magic and that the lubrication engineers haven't worked to make oils better since ZDDP's have started to be phased out. I even got a bunch of SAE papers today on the subject to get some quotes from to try and convince these guys, but they still think that their engines will run better on Shell Rotella T and Lucas ZDDP additive than they will on Motul synth. So I guess its a lost cause.

Don't try to fix stupid.People have tried for years.Don't work.Hillbillies.

Yeah, I guess the old quote is accurate in this instance "A little knowledge is a dangerous thing"

Since there's some proper lubricant discussion going here and the OP has been answered I've got a question for you guys. I've always been told the old story of how it's disaster to swap to a full-synth after years of using dino because it could lead to leaks. Is there any truth to this shit?

I'm getting ready to put my CBX back together(finally) and I've been wondering about the pros/cons of using a good synthetic. The valve seals are new as is every gasket from the engine case up but the side covers are original and since I'm in spec I'm reusing my rings.

You'll be fine Andy. Most of those leaks as far as I can tell are caused because the synthetic is cleaner so the gunk that is sealing old engines gets worn away. If you've rebuilt it and everything she'll be fine. I'm gonna run full synth in my bike after my rebuild, and she's 34 years old.

Theres no other reason I can think of for engines to leak when you switch oil. Synthetic isn't some magical fluid. It's designed to have the same viscosity or whatever, the difference is that its more uniform in molecule size, resists thermal breakdown and wear better than ordinary oil.

See that was always my view. I couldn't for the life of me see any reason it would cause problems unless the detergents and such would clear out crud that was actually maintaining seals.

So where do you guys get your Motul and dare I ask how much it costs?

Honda One sells motul and repsol. 4L jug is about seventy bucks. Ouch I know, but when you're only doing an oil change a year I think its not so bad. You could even get away with changing it every two years on motul but I like to change every spring, since there might have been a bit of condensation over the winter or whatever.

You will be fine Andy I have done it with every bike I own including my KZ and z50.I get motul through Parts Canada.I only use the full syn. Factory Line series 15/50.Twice the price of the regular syn. 80.00 for a 4l If I remember right.I can check today.But way cheaper than main bearings
I like that quote Harry.

Oh you use the 300V factory line? I was gonna buy 7100. Think theres much point in the extra ten or twenty bucks for a road bike?

Motovan's catalogue lists 300V at $79 a bottle, 7100 at $61.

I should get some elf ordered in since I have a blue frame

Once a year Harry???? You're obviously not riding enough

If I manage to get through a season and not crash or take apart my bike halfway through, I might change twice!

I think it's well worth it.I changed mine after every dyno time and race weekend.Filters when ever the pan had fibres in it.I keep 15/50 300v in my streetbike for a full season and it's a built kz 900.No problems after 4 seasons.I ride it hard to say the least.

Cool, I may just go with that then, $20 is not much when you're talking about your engine. And my engine isn't going to be cheap when its finished!