My Clymer manual has a nice section on the basics of working on a motorcycle. It’s well worth reading, at least enough to know what’s in there. I’m guessing a good shop manual will have a section like that in it, no matter what bike you have. If not, you can Google Motorcycle Mechanic Basics, or something similar, to get a feel for the initial issues.
What about the possibility of inadvertently making the motorcycle unsafe to ride? I think this is unlikely. A professional mechanic that gets interrupted and fails to complete something is probably just as big a threat. Is your front wheel going to fall off, for example? No. Take a look at how the wheel is attached to the bike. The axle has about an inch of thread on it. You insert the axle through the wheel bearings and screw it into the left fork. The right side sits in a cradle that has a cap with 4 lock nuts holding it on. A glance at it shows you that it is all intact. Even if everything loosened up, that shaft has to back way out before it would fall off. You would notice it. All you have to do is look at the axle cap and you can see the 4 nuts in place and the end of the axle even with the side of the cradle. All is well.
But it should never loosen up, because you have tightened the fasteners sufficiently to prevent that. Which brings up what is arguably the key issue of bike maintenance. How much do I tighten the fasteners? The simple answer is “a bit more than is needed to keep them from loosening.” In reality, every situation is unique and you are going to have to deal with them accordingly. It helps a lot of you have enough experience to have, sometime in your life, stripped out a screw thread, broken a bolt, and had something fall apart because you didn’t tighten it enough. You would have acquired a certain amount of feel for it. Your brain tells you when to stop tightening.
You can buy one or more torque wrenches and tighten according to the specs listed in your manual. I don’t have a torque wrench, but I plan to get one if I ever do anything inside the engine. I do consider myself to have a pretty good feel for tightening fasteners, though.
You need to pay attention to what materials you are dealing with. For example, the oil drain plug in the sump of the F650 is steel and it threads into the aluminum engine casing. The published torque specs for this fastener were too high and a lot of bikes wound up with stripped out threads in the engine case. BMW came up with a repair kit to replace the damaged threads, using a thread insert. I tighten the plug without a torque wrench and haven’t had any trouble with it loosening up. In fact, I go by feel for all the work I have done. If I were working on a racing bike, I would make use of a torque wrench because higher speeds and vibrations are more demanding.
Aluminum is a lot softer than steel, and hardened steel is stronger than ordinary steel. Cap screws, for example, have a system of marking on them to indicate the level of strength.
The F650 engine is attached to the frame with cap screws and plastic insert locknuts. The plastic deforms as the bolt is threaded through the nut and if the nut comes loose the plastic prevents it from spinning all the way off. The front axle cradle cap uses deformed metal locknuts, meaning the outside end of the nut threads is deformed, creating an interference fit. These nuts will also not spin off the stud if they become loose.
The body panels are attached with large head diameter screws about an inch long. They thread into clip nuts attached to the frame or to a panel. The natural uneven matching of the components creates resistance to coming loose, and you would spot a loose screw long before it fell out. I haven’t had any trouble with these screws loosening up, or any other screws for that matter.
You don’t want your chain to separate while you are riding. It could jam up your rear wheel and cause an accident. When I replaced my chain, I installed one with a master link. I won’t do that again, because I don’t like the little clip that holds the master link together. There is no backup if that clip falls off. And if it falls off the master link will work it’s way apart and the chain will separate. It’s a bit harder to install a new endless chain, but I think it is the way to go.
I’m still in the mode of reassuring that working on your bike won’t make it unsafe to ride. If you look at the F650 rear wheel, the axle has a plastic lock nut holding it on. The nut isn’t going to spin off and it is entirely visible. The axle is captured in the other directions by the mounting, so it can’t separate entirely from the frame. It might get a little loose but the chain tension adjustment screws keep it in place.
The triple tree can’t even begin to separate from the bike because the locknut is essentially in your face at the top of the triple tree. It’s possible one of the tubes could loosen in the triple tree clamps, but there are two clamps on each side and you would notice something wrong because the top of the tubes are visible and you would see the tube sliding up out of the top clamp.
The same situation applies to the handlebars, in that you are looking right at them and would notice anything loose long before it fell apart.