Synthetic motor oil?

There are many, way too many variables to answer this precisely, but in the case of a broken in Majesty (which in and of itself is debatable, I loosely propose 5k miles) a quality synthetic oil "can" and "should" in theory produce longer lasting protection so long as the oil is kept clean. High heat breaks oils down quicker and standard oils presumably start to falter before synthetics in controlled tests, but dirt/blow by/dust is still part of the equation, and that can have a negative effect on folks who run synthetics for double or more miles / time than standard oils, but fail to put new filters on. It really requires oil test sample analysis for your particular riding environment and style to predict which oil might best suit your scoot in terms of cost vs. protection.

In terms of sheer protection, clean oil vs. clean synth oil, probably not worth talking about in terms of difference.

I have never met anyone who can prove one is better than the other in all conditions and I go back and forth (different vehicles) all the time. For my $$ I mostly stick to name brand standard oils and keep the 3k change interval as the target.

Another thing to keep in mind is the Majesty does not run a clutch and transmission in the motor oil. It has separate oil and therefore does not require motorcycle specific blends. So, in theory, using Castrol auto oil, for example, should work just fine, whether you choose synthetics or not.

The next discussion might be the oil viscosity preferences for the Majesty 400 ... 10w40 for better efficiency or 20w50 for more protection ???

Heat is the primary reason for oil break down and loss of viscous protection, but it is not the only reason. Synthetics will hold up longer in heat tests, but unless you are running the machine in stop and go traffic in 90-100 degree temps for hours a day, I doubt that standard oil will fail in the 3k mile intervals.

The liquid cooled AND low heat motor (at reasonable throttle levels) will be easy on the oil. Although I do use synthetic for other bikes (Amsoil for motorcycles in my FZ1) my decision was based on the motors ouput capabilities and the heat generated to do so. High performance motorcycles run a very lean mixture (less gas, more air ... relatively) at higher rpm's (10-12k) and that heat happens immediately! The same just wont happen on a Majesty ... its design is more relaxed, even though it can be quite compentent for what it is.

I have not heard of any case where someone would have saved their motor if they had used synthetic oils. Fact is that most engines today will run way past their target on standard oils. Living in San Antonio, South Texas, I feel that running a slightly thicker oil, like 20w50 gives me more protection than with the 10w40 synthetic, but 20w50 synthetic might do even better. But when you can pull the dipstick out of any vehicle and smell anything other than the original oil you put in, you are witnessing blow by chemicals passed from the combustion chamber into your oil, which is not filtered out effectively and is extremely corrosive to your engines internals. The thicker oil can help reduce blow by on certain motors but it is not a static reference. But no oil can protect from this effect and therefore cannot be left in the motor for too long, even if it is still viscous.

My FZ1 makes a different sound with synthetic oils than standard oils, and if you search the oil posts on the FZ1 board, you will find that most folks have gone to synthetics, but then back to standard because of strange happenings with the motor using synthetics. Some motors just do not like it, and some motors are specifically designed for standard oils (a Toyota article comes to mind). I rode to California and back on a filling of Amsoil 10w40, lost about half a quart somewhere in the middle (common complaint of synth users on FZ1's) and could not find Amsoil dealer anywhere. Had to use an alternate oil, but they have different chemical bases (according to the Motul rep it is not good to mix synthetic oils) and could have created a problem. It didn't but still it was a worry that I will not repeat. Next time, I am going with standard oils ... can find Castrol everywhere. I changed out to Motul standard and haven't lost a drop. Not sure of the science behind that mystery yet ...

I used to have a '91 5.0 Mustang and a magazine did a test on synthetics.
They put a mildly modified 5.0 on a chassis dyno with all petroleum based fluids. Then they changed everything to RedLine synthetic - engine oil, manual transmission fluid, power steering fluid and differential fluid and got a 5% horsepower increase. Of course the Majesty doesn't have a manual transmission, power steering pump or differential but this does prove you can get a small horsepower gain from synthetics.
As for longevity, to me it's a tough question. Engines are so well made today it's rare to wear one out. Do you really plan to keep your Majesty past 50,000 miles? I have a friend with a '94 Magna 750 with over 80,000 miles on it who ha always used petroleum based oil - he changes it and the filter regularly and the engine has never had a problem.
On the other hand the Majesty takes so little oil going with synthetics doesn't add much cost unlike an auto engine that takes 5 quarts.
I'm going to use synthetic in mine after 1,000 miles. Where I think it might help is the final drive oil - that oil is not filtered or cooled.