Motorcycle Repair: 1979 CX500 setting the air/fuel screws, cx500 custom, fuel mixture

Question
Hello Bill,
I recently installed a set of carbs from a donor bike (same
year & model) onto my friends 1979 CX500 Custom. I
thoroughly cleaned the carburators & installed new primary
& secondary jets, as well as pilot screws. I synchronized the
carbs then I attempted to set the pilot screws. The shop
manual recommended 1 & 3/4 turns out to start, the rpm's
dropped as I turned the screws out (enrich), I turned the
screws in (lean) & the rpm's came up all the way until they
were seated. Do you know of any reason why this would
happen. I have performed the aforementioned procedure
on my 1985 VF1100C & have not (knock on wood)
encountered this problem. Any remedy, or advice on this
predicament would be greatly appreciated; I am hopelessly
stumped. Thanks, -Lex

Answer
Lex,  too much fuel or too little air in the idle circuits.

15.5mm float level is critical to correct idle and fuel mixture circuits.
#45 idle jets are standard
#78 primary and #112 secondary main jets are specified.

I have seen examples where people have swapped the pri and secondary mains accidently and then had a lot of richness in the lower engine speeds.

Be sure that your valve clearances are okay and that the compression is close to specs 175-200 psi.

Bill Silver