yep sounds like your secondary side of your carb is a bit crook it will be opening at 4100-4200rpm and causing the sound change in your motor, it sounds like your problem is intermittent but the easiest way to try and fix it would be with some fuel system cleaner and a good going over the carb with some nulon carby cleaner to try and disolve any deposits and help restore normal opperation.
Failing that it could be time for a carby overhaul, about $60-70 for a full kit or maybe get a hold of a weber 32/36 DGV carb and adapter plate if you want a bit extra power

Thanks. I'll check the article.
The dying giraffe sounds to me like a valve opens in the carbie and the engine noise totally changes. Depending on how the engines running sometimes the engine just sounds different or it can sound really loud and really #### but theres a deffinite spot around 4100/4200rpm where something opens up and the engine just goes differently. If it happens in your engine you'd know what I'm talking about.

check your carby floats also

i take it you mean the A14...

yes they should redline at about 6500 so 3000 to 5000 is a safe powerand.

the thing with these engines is overtime they wear out and become "untuned" so to speak...

go to the tech section and find that article about tuning your A series. should help any flat spots.

as for the noise: ive never heard a dying giraffe so i don't know what noise its making... where does it sound like its coming from?

Oh and 14a's redline at 6500rpm don't they?
Mine seems to get its power between 3000 & 5000 rpm so thats usually where I keep it when I'm driving hard but its always nice to be sure you're to over reving the engine.

It seems like I'm asking a new question everyday on here but anyway...
I've got a 120Y with a 14a inside. Last night I took it for a drive thru the hills and there were two things I really noticed.
1. When the engine hits about 4200rpm a valve or something must open and the engine suddenly sounds like a really loud dying baby girrafe. Is this normal? And if it is is there anyway to make it a bit less loud/shit sounding?
2. I was getting random flat spots. When the car was warming up they were between 1 & 2000rpm but then the flat spot seemed to move as I was driving. How can I stop this?
Basically my engine seems to retune itself about every two days and run differently, which gives it new and excitingly different positve and negative characteristics. Is this normal or is it something I can fix?