I think the carbs are clogged with modern fuel, to get my SEI going after a long lay up i do the following;
1) take all 3 float bowls off this can be done with the carbs still on the bike.
2) remove the choke, main and slow running jets being carbs being careful not to mix them up.
3) blow the jets out with an air line to clear crystalised petrol from them( dont poke anything through the jets as this will damage them)
4) reassemble the jets and float bowls.
5) turn fuel on and check for leaks ( try tapping any carbs that flood to free the float this often works)
6) try starting with full choke this should do the trick.
Re the saches ignition to find top dead center you will need a dial guage down cylinder no 1. It is important to set this accurately as mine did not tick over well when i did it a less accurate way.
Good luck might see you at Mallory Park if you can make it.