That makes sense for this other bypass
yeadon_m
I should have typed "single" not "signal".
I think the hole closer to the motor is the "Pilot Outlet" and make sense if you have carb with only one pilot holeI think they wanted less fuel out of hole near slide (Bypass) when it supplies fuel mix, but same out of hole near engine when slides near closed. So they made pilot jet smaller but, had to increase the 0.5 mm to 0.8 mm. 0.5mm may have been limiting factor for that hole (I have increase pilot jet and there is a point bigger sizes makes no difference with air screw adjusting and I have slides all the way down on idle adjust screw). Maybe 25 pilot and 0.8mm is even more fuel than 27.5 and 0.5mm for that hole same or less???
Towards the end of these bikes existence, I think emissions may have been more of a concern than performance. I read somewhere that emission standards are more strict for smaller throttle openings since this is where most people are when street riding. You see 4 stroke bike in the late 70's and early 80s where the pilot jets are pressed in and can't be changed for this reason.
I have access to number drills and reference pins and I am going to check all my pilot holes. If those holes have a rough surface, drag would be very high reducing overall flow.
1.4 mm is ~#54 drill
0.8mm ~#67
0.5mm is ~#76
