After finally getting my rebuilt engine run in, its time to concentrate on the fine tuning. For those of us that are familiar with the Amal concentric carb tuning notes that Jim Bushman wrote, I wonder if anyone can clarify his comment in point 8 of the pilot screw adjustment section. He writes..." When you hear the engine revs race, you want to turn it back a 1/8 to ¼ turn ‐ the sweet spot is not at the extreme" what does he mean by "turn it back" is he saying back it out, or back towards closed. More or less air? I can't figure it out. I wrote to him but no reply. Thanks
His text in point 8: "The pilot jet air screw may be adjusted at this time, but by very little, no more than ½ to 3/4 turn in either direction. The effective range of adjustment for the pilot jet is 1 turn to 2 turns. This is where a bit of skill & experience comes into play. By turning one screw a little at a time with the engine running (on both cylinders) you can gauge any difference in running and find the sweet spot. When you hear the engine revs race, you want to turn it back a 1/8 to ¼ turn ‐ the sweet spot is not at the extreme. The idle may need to be dropped equally again. "
The revs pick up as you…
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Thanks Jon. That's exactly…
Thanks Jon. That's exactly what I needed to know.
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The revs pick up as you weaken the mixture, depending on carb this could be adjusting in or out. When you get to the point the motor starts to pop or run unevenly you have gone too far. Get it to the point of even high revs, then richen the mixture slightly (1/8 - 1/4 of a turn). This will help keep the piston temp down and prevent pre ignition.
The comment on 1 -2 turns I believe relates to the effective range of the adjustment screw.
J