YZ250 - You do realize that the XT250 is basically a low-powered trail bike, right? It was not designed to be flashy or fast.
These machines will run and last forever, even with minimal maintenance. But it was never designed to be fast.
These are the reliable machines that the manufacturers have attempted to associate with the "new" four-stroke motocross bikes. Unfortunately they are worlds apart!
If your brother wants a faster bike he would be well served to sell the XT250 and buy a race bike. it would be very expensive to get this one to be much faster.
Here are few excerpts from a test of that bike;
"Powering the bike is a decent air-cooled 249cc, SOHC four-stroke single, which gets fed through the 33mm Vac carburetor. It seems to be up for the job as it gets 73 mpg, despite the fact that many would feel more at home on a 350cc upgraded version of it. All this baby needs is its 5-speed gearbox and it is good to go forever and ever again. Reliability is not a thing to worry about when buying an XT.
Weighing 291 pounds wet, the quarter-liter Yamaha XT qualifies as an easy to ride motorcycle with a versatile character. We know that because the entry-level Yamaha model has been around for almost three decades now and this is what keeps it going strong.
Launched in the early 1980s, the XT250 had it all with it from the start. The 249cc engine, developing 22 hp at 8,600 rpm, and the five-speed tranny made a good team from the very beginning and the looks of the bike were, as now, the ones of an off-roader.
In 1982, the redesigned XT250 was quite the addition in the Yamaha lineup as it was completely restyled for properly dealing with the rough terrains, making for an ideal farm machine out of the already imposed trail master. Power was reduced that year with fewer revs in favor of engine durability. Apparently, the 17 hp at 7,500 rpm were still enough."
This is a great trail bike. Enjoy it for what it is!