Can't say on the 1300 but on the 1100 it's a 17mm hex. Is the 1300 oil drain an Allen head or a hex?
Go to yur local Lowes or Home Depot (or Sears/KMart or True Value) and get a set of 3/8 drive metric sockets from 8 to ?? (usually 17.) For more detailed work, you'll need a few additional larger sockets, depending on the sizes for things like axle nuts (the rear wheel on a 1300 needs a 17mm Allen on the axle end, don't know what size the nut is.)
Some specialty tools are available from various sources for loan, like wheel bearings and steering bearings. Cheaper to pay postage on those kits than to build yur own.
Also, get a decent set of metric box-open wrenches.
If I was building a new metric tool box right now, I'd go to Lowes. I like the look of their house brand and it's all life-time guaranteed.
Add a few screwdrivers and you'll be good to go for most any maintenance. Probably worth it to find some Japanese Phillips screw drivers, their tip is just a littl different than our 'Merican style. (This little fact helps 'splain why we have all stripped out the heads on Honda screws for years!)
For the high priced spread, go to aerostich.com and buy their titanium stuff. Too Kuul!
For the cheep-cheep cheap, go to Harbor Freight. Save yur money for gas 'n tars.
While yur at it, put together a small kit to carry on the bike. Cruz tools (or Aerostich again) have prepared kits for "on the road." I carry enuff stuff to do virtually all the standard maintenance but most don't need that much. Carry
at least enuff to pull the wheels and/or fix a flat.
(My tool box contains everything from pot-metal junk to NAPA and Craftsman. I can never find what I need and most of what I have never gets used. Can't close most of the drawers on my rolling box because they're stuffed with time-collected tools. I have a separate handled box with all my inch size stuff, still use some of that occasionally but not often. BTW, 1 1/8" is 27mm, 9/16 is 14mm.)
Prolly more than ya wanted to hear but I could go on and on and...