YBR is "plastic"? Lol I had no idea I was riding a "plastic" motorcycle all this time.
What you should know is that there are different polymers of plastic, some are much stronger than others. The plastic cup you see at jumma bazaar is not the same as the plastic used in making , say, a glock-17 ( yeah, there's a gun made of plastic ). The side fairings of Yamaha YBR 125 are made of ABS plastic, which is quite strong in my experience. As a matter of fact, I gave my motorcycle to a friend who rode it with like 20 different people as passengers , 2 at a time! and some of those "pathans" just jumped on the back seat. It's still in perfect condition.
If you are to buy a YBR , go for the YBR-G model. For 3 extra thousand, you get better tires, better front forks, a brighter headlamp.
Regarding mechanics, first of all, the same goes for most new motorcycles, dont let a mechanic touch your bike besides regular maintenance i.e. oil change, airfilter, lubrication etc.
Regarding parts, now there's no shortage of YAMAHA parts in any major cities of the country. I've owned mine since november and have never had to go looking for parts any further than my own city.
You can see my thread in the Yamaha sub-forums here , I thought about changing to CG-125 but the crap they came out with in their 2016 model makes me appreciate the money I spent on my YBR-G.
However, if you want a decent ride, I've seen some very happy people with Suzuki GS-150 for around the same price as YBR-G , except you don't get alloy rims or any decent looks, just your regular suzuki that your abbu jee used to ride when he was 15 years old.
We're planning a road trip to Azad Kashmir insha'Allah next month and the motorcycles going are Yamaha YBR-G, Suzuki GS-150 and Ravi Piaggio Storm ( don't count that one out, it's an excellent bike as well ).
Oh yeah, and if you want speed in a straight line. Go for CG-125, that's all it's good for.