1988 Elite SA50...timing, "air screw" adjustment questions

[ramblerdrver]

I checked the ignition timing today to see if the CDI ignition module was working right on my 1988 Elite SA50 and found the timing was right on the mark...at 1800 rpm and at all rpm's. Is that correct... it doesn't advance with rpm? The carb idle "air screw" adjustment...the name implies you are varing the air that's mixed with the fuel...but is that actually correct? It looks to me that you are actually adjusting the fuel portion...screwing it out increases the fuel flow. Correct, or am I not looking at the passages correctly? Finally...any way to kinow if the muffler is plugging up, without going to expense of buying a new one?

Thanks

[Bear45-70]

Yes, timing is fixed, the CDI does NOT do anything to the timing. The air screw, as the name implies adjust the amount of air being allowed into the idle circuit. The fuel changes due to the increased or decreased in air flow.