My experience with 4 '73 RT3 Enduros and a '71RT1B Enduro is they run good with # 260 main jets (genuine Mikuni). Not sure why Yamaha went with a smaller jet for the '74 (maybe emissions) but the '74 had a reputation for burning a hole thru the top of the piston. Replacement pistons are hard to find today. I'd try it with the 230 or maybe even larger.

If its a "74 as you say in post #4 then be good to change the heading to DT360A.
Just researching & 180 is std in "74.
Credit there to PABDT in post #9.
www.yamaha-enduros.com/index.php/service...ctory-service-manual
Check out page 100 [or 99 if i'm looking at the wrong end of page numbers]. Be other useful info there for you too i hope. Just be aware it covers 250 & 360. The 250 has points ignition if you go there.

1974 DT360 was a nearly complete redesign, not much in common with the earlier RT series. 

It would be a good idea to positively identify what you have by the VIN numbers or it might be a little like trying to repair a Chevy using Ford manuals, specs, and parts.

Sorry, i updated the original post to clarify its a 74 DT360.
I know nothing about these modern bikes.

Doug

I changed the topic title for you

I just got a '74 360 as well, found this after reading about it here

mikunipower.com/Manuals/VM_Manual.pdf

After a night smothered in charcoal briquettes, it burned down and this morning I pulled it out, tried water first, it flowed right thru it, unlike yesterday. Bolted it on, and it runs great. Really a fun bike, and a good bit of power. I'll see if i need to swap the jets after I ride it a bit.
Thanks for all the tips!

Doug