alfred e numan
Senior Member
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- 1,325
The idea for this came from a paragilder err- ultralite aircraft site. On the well lighted side of the bore on the 990 you can see a dot. There are 2 more dots hidden in the upside down U shaped shadow. These " dots " are holes- the fuel jets for the low speed -midrange circut on the 990. The shadow you see is the reflection from a polished HY 30 cc factory carb - y if you are in AU. The Hy carb has a U shaped notch. The idea is- the notch causes a stronger air flow across the 3 low-mid circut at idle and slightly off idle openings. This is what the ultra lite fellow says happens - improved hot-cold starts, You have to lower the idle speed screw- slow the rpm down and feed more fuel with the low speed adjustment screw. -- less low-mid starvation of fuel. I will see -- as soon as time and weather allows. This factory notch is small - but i have dremel-red loktite and screws. - never pry-pull on the butterfly valve- when r-r is correct the valve will fall out- drop in to place easly.-- In the morning i will wet test with viberation and read the pop off pressure.