Aye Freddie,
Welcome to the forum, I used to own an AJS 18S 1953 as a workhorse in the mid '70's. At one time putting a 1,000 miles a month on the speedo. The Achilles heel for me was the dynamo chain tangling with the primary chain!

As for your query about the Suzuki 'Tempter' 400 (bit like a Savage LS650); who do they find to dream these names up? I have done a bit of Googling and may I suggest you have wee looksee at these links below. It appears that Clymer print a manual for the Suzuki LS650 Savage and whilst the cc are different, I have found that Japanese market 400cc sleeved down versions of their 650cc machines are very similar in construction/torque values and parts diagrams.
Link to a website of Suzuki manuals:
Suzuki_manual_list_websiteScroll down the website and you will see a green button 'link' with "Suzuki LS400 Savage LS 400 Illustrated Parts List Diagram Manual" written next to it. If you click on the link:
Suzuki_LS_400_Parts_list it allows you to open and download from a 'Compressed (zipped) Folder' the "LS400 Illustrated Parts List Diagram Manual 1987" jpeg and gif images, the Acrobat link doesn't appear to work!
This is the link to the Clymer website from where the Suzuki LS650 manual may be purchased directly:
Clymer_Suzuki_LS650_manualI use Clymer manuals for both Yamaha XT600E (SRX600, XT600 and XT600E motors), Ducati single cylinder 250-350-450 narrowcase and widecase engines (along with the Haynes widecase manual) and a Honda factory BROS 650 workshop manual for a BROS 400, with no problems.
Hopefully, this will get you started and that you won't need to do any major engine rebuilds just yet!

My regards, Bill