Can you give us a little more information? Did you get this from the bike itself or the title? A picture of the bike would help.
Giving us the year of manufacture will help in narrowing down this mysterious 4T4 code that keeps coming up in Canada. Assuming it is a Canadian bike there should be a label on the steering neck that shows the date of manufacture. For example, my 1982 Heritage Special shows; "MFD BY YAMAHA MOTOR CO LTD 9/81". There should also be the 3 digit model code and then the serial number on the bottom of that label. In my case when the bike was painted the label was painted over so I had to carefully scrape the paint off. Just below that label the model and sequence number for the bike should be stamped right into the right side of the neck as well. That number also shows up on the engine just above the kick starter.
There seems to be a few Canadian owners that have posted the 4T4 code before but no one has consistently told us where they got the code from.

There are many model lists out there but most are incomplete and also have some inaccuracies. For example, the list I use the most shows my bike as "14V" when it should be "14W".
The possibilities are;
i) If it is stamped on the neck or engine then we may have an oddball Canadian only code.
ii) The current lists are missing this model designation or have the wrong code for it.
iii) If it is from the title or registration...........well, back in the 80's they were still typing the titles in most jurisdictions. If you look at your keyboard you will notice that the "T" is right next to the "R". "4R4" is a valid code for a 1981 XS400SH Heritage Special.
Are there any other Canucks out there with a 4T4 code that care to weigh in? Maye we can get to the bottom of this one.