This oil is jaso approved. It would be very suitable for a 400ex or 450r oil. Shell rotella is very similar and has been in all of my honda 400 and 450s for 10 years and hundreds of hours.
Where did you find the JASO rating on this oil? The only ratings I was able to verify was the API "C" (diesel rating) - go here to view the technical data sheet - no where on it is a JASO rating https://www.schaefferoil.com/documents/299-700-td.pdf
Shell Rotella T4 is not JASO rated either - here's the tech data sheet for Rotella T4 https://rotella.shell.com/en_us/prod.../t4-10w-30.pdf
Like I said, you can use it if you want to, but it may not be the best oil for the application - just because you haven't had a problem does not mean the oil is performing satisfactorily. You use whatever oil you want to and I will use the recommended lubricants. You do it your way and I'll do it my way and we'll all be happy.
Note - the 450 uses separate oil in the engine and transmission - the 400 uses the same oil to lubricate the transmission and the engine.
Both Rotella T and the above listed oil meet or exceed Jaso ratings. The link you provided to the shell rotella tech sheet in fact says on the bottom left in bright yellow the ratings. Jaso is listed. I have been running shell rotella for a long time and have discussed it's properties with clutch manufacturers as well as engine builders.
Did you know that Rekluse clutch even recommends running this in the clutch side? here is a link to that
Rekluse Support FAQs
I am fully aware that the trx450r has separate oils, this allows the owner to be able to run their preferred oil on either side. The fact that I have pulled apart many engines after running rotella T and have seen very minimal wear will prove that it's more than satisfactory. I will also mention that there are an abundance of other riders/racers who run this oil. It is no secret.
I am going to provide a link to the Schaeffer oil website it is the same as yours. I am not sure if you are missing the specifications or intentionally ignoring them, however I do feel it is beneficial to make sure we are correct in what we say. The OP's listed oil does meet JASO standard and likely exceeds it. https://www.schaefferoil.com/documents/299-700-td.pdf
SynShield™ Durability Advantage SAE 15W-40 meets and exceeds the following manufacturers’
specifications and requirements: API Service Classifications CK-4/CJ-4; Military Specification MIL-PRF2104K;
ACEA E7-12; ACEA E9-12; Global Specification DHD-1; Caterpillar ECF-3; Cummins CES 20081,
CES 20086; Detroit Diesel Power Guard Oil Specifications: DDC93K218 and DDC93K222; Deutz DQC
III-10 LA; Ford WSS-M2C171-E, WSS-M2C171-F1; JASO DH-2; Mack EO-O Premium Plus, Mack EOS4.5;
MAN 3275, MAN 3575; MB 228.31; MTU 2.1; Renault VI RLD-3, RLD-4; Volvo VDS 4, VDS 4.5;
Navistar; John Deere; CHN (Case-New Holland).