Hi again!
I couldn't work on the engine, but I've been able to solve a couple of things. [&:]
The engine DOES have a working pulse hole. Right under the intake port there's a hole, which is routed through the carb spacer and then goes into the carb (small hole between throttle arm and intake nipple, the other one near "mexico" is closed).



I found how to tap the hole in this link. The hole is 4.22mm wide; I'm a bit worried that there might not be enough thickness to make the same 10-32 tap (~5mm), but if it worked for them, it should work here too. Regarding the set screw, they're chromed and have a small chamfer at the end. Is it a good idea to grind the end straight, or it's just unnecesary work (or even worse, making it easier for the coating to come off)?



As for the carb spacer, if I got it right, it must match exactly the shape of the intake port and the diameter of the carb (mine is around ~15.88mm on the engine side, and has a 12.7mm venturi), isn't it?
Would be of any help to smooth the path along the spacer?



Again, I'm sorry if I'm making dumb questions or being too picky, I've never "played" with engines at this level and I'm not familiar with things. [:'(]
See you!