It's in the service manual.
Vm26ss on a 900a4
Pilot 17.5, main 115.

If you don't have a copy try downloading.
https://kzrider.com/service-manuals

They appear to be vm26ss. Oddly appear to be fuel screw only, no air screw?
Not sure what make/model/market they were fitted too.
Just too confuse some Vm26 have both air and fuel screws!

Allen's performance will have the genuine mikuni emulsion tube you require.
https://www.allensperformance.co.uk/shop/

27mm on the engine side means they will be 26 mm at the slide as they taper slightly. These were fitted to 900 a4's and early z1000's. Easy way to tell difference between 26mm and 28mm is the mix chamber cap on 26 is domed and 3 screw. 28mm are flatter and slope towards the engine side with just 2 s...

Finding them can be difficult. Problem is points/condensers are old tech. As such they get bought from the cheapest supplier and as the market is decreasing decent manufacturers can no longer justify manufacturering them. Consequently China jumps in and makes cheapo copies. Original denso ones have ...

Oggers, just a bit of a heads up. If those condensers are Chinese they only seem to last about 6 months before crapping out.
Try to find some Japanese denso ones and get them for future stock.

Price

Presumably the back plates are stamped out. It would be simple to add an embossed "front" or "back" mark to the process.

Oggers responded to your pm

Correct.

For it to provide a permanent earth through the failure unit it would show continuity across the terminals wouldn't it?

If its on all the time Where's is the idiot light earthing? Is the rear brake light on/ operating cofrectly? Could be as simple as rear brake switch needs adjusting. What happens if you disconnect the failure unit? If you do that the idiot light will only come on when your front or rear brake is app...

Remove tail/brake bulb. Idiot light should flash.

Assuming that ebay one works that's cheap.

20 is caning it mpg. 35 to 40 should be achievable on normal riding depending on engine air and exhaust set up.
Motorways are not good on 650's with standard gearing which is fairly low.