Bert Otten wrote:
> What is exactly the difference between FX, No.5 and No.6 needles?
Geoff Love wrote:
> Unfortunaty, I havent been able to find any definitive info on the dia.
> of one needle at a certain point along its length.
Maybe I can shed some light:
S.U. Needles have two types of shoulders- square and tapered. Starting at the
square shoulder on one and at the lower taper end of the other, the needle is
indexed at 1/8 inch incriments down the length to the small end.
My list includes all needles extant from 1933 to Sept. 1959 and the FX is not
included. However the 5 amd 6 needles are, and suffice it to say, they are
identical at the first four 1/8 inch indexing points, when at the fifth point
No.6 becomes one ten thousandth richer and so on down to the end where No.6 is
six thousandths richer than No.5. One could assume that thay would perform the
same getting off the mark but from mid-range on No.6 would be slightly richer.
Quick fix- Try 30 weight oil, or if you have access to other springs you
might try Red rather than Blue. Red is 4 1/2 oz. load and Blue 2 1/2 oz.
Not to be preachy- and I am sure you know all this- but however enticing it
may be to start tinkering with needles, please do not lay a glove on the carbs
until you are absolutly sure everything else is dead on. Otherwise you are
floundering around without a base line.
If you and Geoff Love contact me- or anyone else who cares to- maybe I can
come up with something more helpful.
Ralph Cadwallader Lakewood, OH
72GT 66 4/4 68 FBird Old age and treachery will prevail.