The older TTRs had grease nipples fitted but later ones do not. I guess the bean counters at Yamaha decided to shave a few yen off the overall production cost
It is possible to retrofit the old linkage parts but getting hold of them in good condition might be a challenge.
The alternative is to strip the linkage down and clean/regrease on a timescale that suits your riding and terrain. If you ride wet and muddy lanes in the UK and have to put your TTR away wet then clearly such work would be required more regularly.
Thank you Brian . Just had a look on Google to see where the grease nipples where on the older ones . I work in Engineering, so next week I'll be doing some home work and fitting grease nipples