The only real issue with N400 is the 2018/2019 clutch has an issue where it is limited to a small amount of wear before it starts slipping.
However, the parts to fix this if you buy a 2018/2019 is just $50 plus maybe a gasket and an hour or two of time -- so it is no big deal.
Just keep your clutch cable adjusted properly to 2-3mm of freeplay and you might get by with nothing.
A secondary issue a few folks who ride hard have is with a coolant seal eventually failing.
Again, the parts to fix this are cheap, but a bit more labor and gasket cost for this job.
Otherwise the bike is pretty solid and simple and fun.
However, the parts to fix this if you buy a 2018/2019 is just $50 plus maybe a gasket and an hour or two of time -- so it is no big deal.
Just keep your clutch cable adjusted properly to 2-3mm of freeplay and you might get by with nothing.
A secondary issue a few folks who ride hard have is with a coolant seal eventually failing.
Again, the parts to fix this are cheap, but a bit more labor and gasket cost for this job.
Otherwise the bike is pretty solid and simple and fun.