Kind of sad to be comparing little toy bikes in this day when so much more is available, but having lived through the age of import barriers and even martial law, I will indulge you for the sake of nostalgia!
I owned three or four NSRs, mostly concurrently, one of them for 10 years, and used to rebuild tune and tweak them for friends. I’ve worked on many FZ/FZR/Breeze models but never owned one.
NSR is pretty tiny. If you’re a big or tall guy, get the Yamaha. It’s much heavier than it should be, the frame being a copy of the JDM/EDM aluminium design, but in thick, heavy steel tube. OTOH, no matter how hard you crash them it’s almost impossible to bend that frame. There are much better rear shocks available now but the forks are so weak you are best served by junking the whole front and grafting something better on there.
The NSR makes about 24bhp stock and can be tweaked to give 30bhp reliably and maybe 35bhp if you don’t care about overhaul interval.
NSR parts are getting very rare and many parts can only be ordered from Thailand. Body panels etc. you mind find unobtainable from any source.
The Taiwan production NSR150 has an aluminum cylinder with cast-in iron liner. While it’s not of bad quality the quality of available oversize pistons is really poor, typically lasting only 10~15,000km. There used to be a Wiseco forged piston available but most machine shops would fit them too tight and they would fail. The usual replacement path is the 125cc cylinder from Thailand which is a coated bore, which unless you have a bad seizure will last forever. Just keep replacing the pistons and rings. It’s counter-intuitive but the 125cc has more performance potential than the 150cc Taiwan item. Kymco did not increase the outer dimensions of the cylinder casting when increasing the bore and as a consequence the area of the transfer ports is reduced to the point where they cannot support the needed time-area to effectively fill the cylinder at higher rpm. However, the Kymco ignition box retards ignition timing beyond 9,000rpm which means it cannot take full advantage of the Thai cylinder’s potential. You can buy aftermarket CDI boxes or perhaps use the Honda Thailand item.
There is one bearing in the gearbox which is a completely non-standard size and cannot be purchased on the open market, and Honda dropped the part from their stock list. If this fails you need to have adapters made or have a larger bearing ground to size. Built-in obsolescence at it’s finest.
Earlier models have smaller fairings and engines straight from Japan… much better quality. Early ones have ‘Honda Racing’ cast into the alternator cover. Later ones have ‘KYMCO’ there.
Later models have big, ugly fairings / body parts and EGR. Power is reduced a bit from the early ones. There is a revised RC valve computer at some point which cycles the valve at lower rpm just to make sure that people who never run the engine hard or use crap oil don’t get the valve stuck. This ruins torque and tractability at low revs but it reduced warranty claims. Sadly, KYMCO did not change the part number so there is no way to tell them apart from the case.
One thing to be very wary of when buying an earlier model is the instrument cluster. Early bikes had the oil level warning system wired differently to the later ones. Although the later clocks are plug and play on the earlier model, and the oil level will test on and off at start-up, the switch in the tank will not trigger the warning light when the tank is empty. Ask me how I know this.
The Yamaha makes 17bhp stock and you won’t get anything more out of that without increasing cylinder capacity. Even you bump it to 250cc it’s still pretty slow. The motor is massively undersquare, which helps low-end torque. Despite it revving to 11k or so it’s pretty gutless. The engine is based off the JDM SRV250, a retro-styled bike. Basically it was massively de-stroked to make 150cc. Heads and cylinders are the same, as is the crankcase and possibly the pistons, so you can drop the SRV crank and rods straight in to bring it back to 250cc. There was also a 250 Virago in Japan which had the same internals, though it only had a single carb. There are other kits which open it up further to 300cc or I think even 330cc. I stopped paying attention a long time ago. One problem with these kits is balance. The JDM bikes all had rubber engine mounts to keep the vibration down. The Taiwan 150cc models have such a short stroke they are very smooth. Put the 250cc guts into your FZ* and it buzzes pretty well. White fingers and numb feet on longer rides.
There was a revision fairly early in the model lifespan which added an oil cooler. Doesn’t seem to make any difference to reliability.
Yamaha build quality is way better than Kymcos, especially evident in suspension, brakes and wheels.
Yamaha parts, at least engine and cycle parts are more available since production went on a lot later.
Only the FZR has a rear disk brake, the others have drums back there which only seem to make noise rather than any brake torque…
There is a 3rd alternative, though I haven’t seen one in many years. There were some Suzuki RG125 Gammas on the market back in the day, though they weren’t popular and I don’t think too many were sold. The FZR and the later NSR were built to look much bigger than they were, and sold much better. The Suzuki was tiny with skinny tires, and despite being faster and lighter than the competitors, no-one really wanted it. Engines, electrics, suspension and brakes were all imported from Japan btw. 25bhp out of the box and high build quality. 250 Gammas used two of the same top-ends and are easily tuned to 70bhp or more. It makes sense a 125 can make 35bhp properly tuned.
Personally, I feel a crotch-rocket is all about speed and noise. The FZR kind of looks the part but regardless of the money you spend on it, it will not keep up with a healthy NSR. Unless you are a big heavy rider, a well-sorted NSR will give much bigger bikes a run for their money in the mountains or a tight circuit.
Threads of note on these bikes: